Hantavirus

Introduction

Disease History, Characteristics, and Transmission

Scope and Distribution

Treatment and Prevention

Impacts and Issues

BIBLIOGRAPHY

Introduction

During the 1950s, more than 6,000 United Nations military personnel serving in Korea were stricken by a mysterious illness characterized by high fever, kidney failure, and spontaneous bleeding. Few realize that this disease continues to claim victims in the region, with 418 cases reported in 2006 alone. Eventually a group of viruses was identified as the cause of this “Korean hemorrhagic fever” and [the group] was named Hantaan virus, after the Hantaan River, which flows through Gangwon and Gyeonggi Provinces.

Subsequently, similar illnesses of varying severity in Asia and Europe were found to be caused by a number of distinct viruses, and the group came to be known as the Hantaviruses. In 1993, a new illness was reported in the southwestern United States. Unlike the Korean disease, prominent features included rapidly progressive lung infection with high mortality (death rates). Despite the unique nature of the disease, a viral agent was discovered which had all of the common biological features of the older Hantavirus group. The new illness was therefore referred to as Hantavirus pulmonary syndrome (HPS). 396 cases were reported by 32 American states as of July 6, 2005, including 142 fatal cases. As in the Asian variety, a large number of additional Hantavirus species have since been identified in the United States, as well as Central and South America.

Disease History, Characteristics, and Transmission

Regardless of differences in clinical presentation and geographic occurrence, all of the Hantaviruses are found in rodents. Man acquires the disease through inhalation of dried rodent excreta, or occasionally through ingestion of milk and other foods that had been contaminated by these animals. In fact, the ability of the virus to survive in dust and the contagious nature of infected material have suggested Hantaviruses as potential agents of biorerrorism.

Scope and Distribution

The following is a summary of the clinical features, distribution, and epidemiology (patterns, characteristics, and causes) of Hantaviruses that infect humans. Specific viruses (strains, or types) are arranged alphabetically.

Old World Hantaviruses

Clinical features Infection by the European and Asian Hantaviruses is characterized by sudden onset, with intense headache, backache, fever, and chills. Hemorrhage is manifested during the febrile phase as a flushing of the face or injection of the conjunctiva (membranes lining the eye) and mucous membranes. A petechial rash (tiny, red dots) may appear on the palate and axillary (underarm) skin folds. Extreme albuminuria (protein in the urine), typically appearing on the fourth day, is characteristic of severe hemorrhagic fever renal syndrome (HFRS).

As the febrile (with fever) stage ends, hypotension (low blood pressure) may develop and last for hours to days, accompanied by nausea and vomiting. One-third of deaths occur during this phase, related to vascular leakage (bleeding) and shock. Approximately 50% of deaths occur during the subsequent oliguric phase (when the kidneys produce very little urine). Patients who survive and progress to the diuretic phase show improved renal function, but may still die of shock or pulmonary (lung) complications. The final (convalescent) phase can last weeks to months.

Case-fatality rates (rates calculated to show the severity of disease; the number of deaths divided by number of cases expressed as a percentage) range from less than 0.1% for hemorrhagic fever renal syndrome (HFRS) caused by Puumala [PUU] virus to approximately 5% to 10% for HFRS caused by Hantaan (HTN) virus.

Epidemiology Dobrava/Belgrade virus causes severe hemorrhagic fever with renal (kidney) syndrome. The reservoirs (organisms that maintain the infective agent), Apodemus flavicolis (the yellow-necked mouse) and Apodemus agrarius, are found from England and Wales, through northwest Spain, France, southern Scandinavia, European Russia to the Urals, southern Italy, the Balkans, Syria, Lebanon, and Israel.

Hantaan virus causes epidemic hemorrhagic fever (Korean hemorrhagic fever and hemorrhagic fever with renal syndrome). The reservoir, the striped field mouse (Apodemus agrarius), is found in Central Europe south to Thrace, the Caucasus and Tien Shan Mountains, the Amur River to East Xijiang and East Hunnan, West Sichuan, Fujian, and Taiwan.

Puumala virus causes nephropathia epidemica (a usually less severe form of hemorrhagic fever). The reservoir, the bank vole (Clethrionomys glariolus) is found in the West Palearctic from France and Scandinavia to Lake Baikal, south to northern Spain, northern Italy, the Balkans, western Turkey, northern Kazakhstan, the Altai and Sayan Mountains, Great Britain, and southwestern Ireland. The house mouse (Mus musculus) is implicated in Serbia, and Clethrionomys rutilis in western Russia. The muskrat (Ondatra zibethicus) has been implicated as a disease reservoir in Germany. Note that Puumala virus may remain infective in the environment for as long as 12 to 15 days.

Saaremaa virus has been associated with human disease in Estonia, and is closely related to Dobrava virus.

Seoul virus causes less severe hemorrhagic fever with renal syndrome. The reservoir rat (Rattus norvegicus) is found worldwide. Wounds inflicted by other rats appear to be a major source for transmission among rats.

Thailand virus has been identified in humans and bandicoot rats (Bandicota indica, B. savilei) in Thailand.

Note: There are no proven cases of Hantaan or Seoul virus infections either from Europe or from western Russia (west of the Urals)—as of 2000, all claimed cases have turned out to be caused by Dobrava virus. Dobrava virus has been confirmed in the former Yugoslavia, Albania, Greece, Germany, Estonia and Russia. This is in contrast to the Balkan region, where Dobrova virus seems to be carried mainly by Apodemus flavicollis. In Estonia and Russia, the virus has only been found in Apodemus agrarius.

WORDS TO KNOW

CASE FATALITY RATE: The rate of patients suffering disease or injury that die as a result of that disease or injury during a specific period of time.

HEMORRHAGIC FEVER: A hemorrhagic fever is caused by viral infection and features a high fever and a high volume of (copious) bleeding. The bleeding is caused by the formation of tiny blood clots throughout the bloodstream. These blood clots—also called microthrombi—deplete platelets and fibrinogen in the bloodstream. When bleeding begins, the factors needed for the clotting of the blood are scarce. Thus, uncontrolled bleeding (hemorrhage) ensues.

RESERVOIR: The animal or organism in which the virus or parasite normally resides.

STRAIN: A subclass or a specific genetic variation of an organism.

Hantavirus pulmonary syndrome

Clinical features The typical illness is characterized by fever, chills, headache, and occasionally gastrointestinal symptoms. Five days after onset, patients develop dyspnea (difficult breathing), with rapid progression to pulmonary edema/ARDS (adult respiratory distress syndrome) within as little as 24 hours. Recently, cases of prodromic infection (having symptoms of oncoming disease) without severe pulmonary disease have been reported.

Epidemiology Andes virus is transmitted by the long-tailed pygmy rice rat (Oligoryzomys longicaudatus), found in the north central to southern Andes, approximately 50 degrees S latitude, in Chile, and Argentina (and possibly Uruguay).

Bermejo virus (reservoir Oligoryzomys species) has been associated with human infections in Bolivia.

Bayou virus is transmitted by the rice rat (Oryzomys palustris) in Louisiana and eastern Texas.

Black Creek Canal virus is transmitted by the cotton rat (Sigmodon hispidus), found in the eastern and southern United States from southern Nebraska to central Virginia, south to Southeastern Arizona and peninsular Florida; and from central to eastern Mexico through Central America and central Panama to northern Colombia and northern Venezuela.

Cano Delgadito virus (clinical significance unknown) is found in rodents in central Venezuela.

Central plata virus is associated with human infections in Uruguay, and is transmitted by the yellow pygmy rice rat (Oligoryzomys flavescens).

Choclo virus (reservoir Oligoryzomys fulvescens)is implicated in human infections in Panama. Calabazo virus (clinical significance unknown) has been identified in Zygodontomys brevicauda in Panama.

Convict Creek virus (similar, possibly identical to Sin Nombre virus) has been identified in California, and was implicated in a fatal case in Ontario, Canada.

Juquitiba virus, Ararquare virus and Castelos dos Sonhos virus have been implicated in human infections in Brazil; HU39694 (yet unnamed) in Argentina—reservoirs unknown.

Laguna negra virus has caused human disease in Argentina, Chile and Paraguay, and is transmitted by the vesper mouse (Calomys laucha). This rodent is found in northern Argentina and Uruguay, southeastern Bolivia, Chile, western Paraguay, and west-central Brazil.

Maporal virus (clinical significance unknown) has been identified in the fulvous pygmy rice rat (Oligoryzomys fulvescens) in western Venezuela.

Monongahela virus (similar, possibly identical to Sin Nombre virus) is found in the eastern United States and Canada, and carried by the white-footed mouse (Peromyscus leucopus) and possibly P. maniculatus nubiterrae.

New York-1 virus is transmitted by the white-footed mouse (Peromyscus leucopus), found in the Central and Eastern United States to Southern Ontario, Southern Alberta, Quebec and Nova Scotia; and Northern Durango and along the Caribbean coast of Mexico to the Isthmus of Tehuantepec and Yucatan Peninsula.

Oran virus (reservoir Ol. Longicaudatus), Lechiguanas virus (reservoir Or. Flavescens) and Andes virus (reservoir Ol. Longicaudatus) are found in Argentina.

Rio Mamore virus (reservoir Neacomys spinosus) has been associated with human infections in Peru.

Sin Nombre virus is transmitted by the deer mouse (Peromyscus maniculatus) in the southwestern United States. The reservoir is found from the Alaska panhandle across Northern Mexico, Canada, most of the continental United States, to southernmost Baja California and north central Oaxaca, Mexico. The mouse itself shows evidence of pneumonia. The virus has also been found in Pe. boylii, Pe. truei, Reithrodontomys spp., Mus musculus and Tamias spp.

Treatment and Prevention

Although the viruses in this group can be cultivated using standard techniques, viral culture is limited to a small number of institutions which meet strict standards of bio-safety. Diagnosis can also be established through testing for serum antibodies in specialized laboratories. Treatment is directed at support of renal, pulmonary and other systems affected by the viruses. The value of specific antiviral agents is not proven, but some authorities have suggested Ribavirin in the treatment of the Old Word Hantaviruses. A vaccine (Hantavax) has also been developed for the Old World variety.

Impacts and Issues

The Hantavirus pulmonary syndrome (HPS) was first identified as such in May 1993, in the so-called “Four Corners” region of the United States, where the states of New Mexico, Utah, Arizona, and Colorado meet. Initially, it was unclear what was able to quickly kill healthy adults in this region. Virologists from the U.S. Center of Disease Control (CDC) used techniques that allow an analysis of a virus at the molecular level, to link the pulmonary illness to a previously unknown type of hantavirus, which was later named Sin Nombre (Spanish for without name).

In addition to molecular and clinical studies, scientists are studying HPS through the study of rodent populations (which often requires the trapping and collection of various mice species), weather patterns, and climate change, Research in the southwestern United States has linked the years having higher levels of precipitation with a larger population of rodents, as the moisture leads to a greater supply of food for rodents, as well as higher vegetation growth, which provides ample habitat and protection for the rodents. Associated with the weather phenomenon El Niño in 1991 and 1993, rainfall levels increased in the southwestern United States. The population density of deer mice in New Mexico then increased from one deer mouse per hectare (2.47 acres) to twenty to thirty per hectare during that time period. It is thought that this large population of mice led to the first identified outbreak of HPS in May 1993.

Although rare, HPS has since been found throughout the United States. As of May 2007, rodent control remains the primary defense against the hantavirus.

See AlsoEmerging Infectious Diseases; Hemorrhagic Fevers.

BIBLIOGRAPHY

Books

Harper, David R., and Andrea S. Meyer. Of Mice, Men, and Microbes: Hantavirus. Burlington, MA: Academic Press, 1999.

Leuenroth, Stephanie J. Hantavirus Pulmonary Syndrome (Deadly Diseases and Epidemics). New York: Chelsea House, 2006.

Periodicals

Kreeger, Karen Young “Stalking the Deadly Hantavirus:

A Study in Teamwork.” The Scientist. 8 (July 1994): 1–4.

Web Sites

Centers for Disease Control and Prevention. “All About

Hantaviruses.” <http://www.cdc.gov/ncidod/diseases/hanta/hps/index.htm> (accessed May 10, 2007). (accessed May 10, 2007).

Stephen A. Berger

Hantavirus Infections

Definition

Hantavirus infection is caused by a group of viruses that can infect humans with two serious illnesses: hemorrhagic fever with renal syndrome (HFRS), and Hantavirus pulmonary syndrome (HPS).

Description

Hantaviruses are found without causing symptoms within various species of rodents and are passed to humans by exposure to the urine, feces, or saliva of those infected rodents. Ten different hantaviruses have been identified as important in humans. Each is found in specific geographic regions, and therefore is spread by different rodent carriers. Further, each type of virus causes a slightly different form of illness in its human hosts:

• Hantaan virus is carried by the striped field mouse, and exists in Korea, China, Eastern Russia, and the Balkans. Hantaan virus causes a severe form of hemorrhagic fever with renal syndrome (HFRS).
• Puumula virus is carried by bank voles, and exists in Scandinavia, western Russia, and Europe. Puumula virus causes a milder form of HFRS, usually termed nephropathia epidemica.
• Seoul virus is carried by a type of rat called the Norway rat, and exists worldwide, but causes disease almost exclusively in Asia. Seoul virus causes a form of HFRS that is slightly milder than that caused by Hantaan virus, but results in liver complications.
• Prospect Hill virus is carried by meadow voles and exists in the United States, but has not been found to cause human disease.
• Sin Nombre virus, the most predominant strain in the United States, is carried by the deer mouse. This virus was responsible for severe cases of HPS that occurred in the Southwestern United States in 1993.
• Black Creek Canal virus has been found in Florida. It is predominantly carried by cotton rats.
• New York virus strain has been documented in New York State. The vectors for this virus seem to be deer mice and white-footed mice.
• Bayou virus has been reported in Louisiana and Texas and is carried by the marsh rice rat.
• Blue River virus has been found in Indiana and Oklahoma and seems to be associated with the white-footed mouse.
• Monongahela virus, discovered in 2000, has been found in Pennsylvania and is transmitted by the white-footed mouse.

Causes and symptoms

Hemorrhagic fever with renal syndrome (HFRS)

Hantaviruses that produce forms of hemorrhagic fever with renal syndrome (HFRS) cause a classic group of symptoms, including fever, malfunction of the kidneys, and low platelet count. Because platelets are blood cells important in proper clotting, low numbers of circulating platelets can result in spontaneous bleeding, or hemorrhage.

Patients with HFRS have pain in the head, abdomen, and lower back, and may report bloodshot eyes and blurry vision. Tiny pinpoint hemorrhages, called petechiae, may appear on the upper body and the soft palate in the mouth. The patient's face, chest, abdomen, and back often appear flushed and red, as if sunburned.

After about five days, the patient may have a sudden drop in blood pressure; often it drops low enough to cause the clinical syndrome called shock. Shock is a state in which blood circulation throughout the body is insufficient to deliver proper quantities of oxygen. Lengthy shock can result in permanent damage to the body's organs, particularly the brain, which is very sensitive to oxygen deprivation.

Around day eight of HFRS, kidney involvement results in multiple derangements of the body chemistry. Simultaneously, the hemorrhagic features of the illness begin to cause spontaneous bleeding, as demonstrated by bloody urine, bloody vomit, and in very serious cases, brain hemorrhages with resulting changes in consciousness.

Day eleven often brings further chemical derangements, with associated confusion, hallucinations, seizures, and lung complications. Those who survive this final phase usually begin to turn the corner toward recovery at this time, although recovery takes approximately six weeks.

Hantavirus pulmonary syndrome (HPS)

Hantavirus pulmonary syndrome (HPS) develops in four stages. They are:

• The incubation period. This lasts from one to five weeks from exposure. Here, the patient may exhibit no symptoms.
• The prodrome, or warning signs, stage. Symptoms begin with a fever, muscle aches, headache, dizziness, and abdominal pain and upset. Sometimes there is vomiting and diarrhea.
• The cardiopulmonary stage. The patient slips into this stage rapidly, sometimes within a day or two of initial symptoms; sometimes as long as 10 days later. There is a drop in blood pressure, shock, and leaking of the blood vessels of the lungs, which results in fluid accumulation in the lungs, and subsequent shortness of breath. The fluid accumulation can be so rapid and so severe as to put the patient in respiratory failure within only a few hours. Some patients experience severe abdominal tenderness.
• The convalescent stage. If the patient survives the respiratory complications of the previous stage, there is a rapid recovery, usually within a day or two. However, abnormal liver and lung functioning may persist for six months.

Diagnosis

Serologic techniques help diagnose a hantavirus infection. The patient's blood is drawn, and the ELISA (enzyme-linked immunosorbent assay) is done in a laboratory to identify the presence of specific immune substances (antibodies)—substances which an individual's body would only produce in response to the hantavirus.

It is very difficult to demonstrate the actual virus in human tissue, or to grow cultures of the virus within the laboratory, so the majority of diagnostic tests use indirect means to demonstrate the presence of the virus.

Treatment

Treatment of hantavirus infections is primarily supportive, because there are no agents available to kill the viruses and interrupt the infection. Broad-spectrum antibiotics are given until the diagnosis is confirmed. Supportive care consists of providing treatment in response to the patient's symptoms. Because both HFRS and HPS progress so rapidly, patients must be closely monitored, so that treatment may be started at the first sign of a particular problem. Low blood pressure is treated with medications. Blood transfusions are given for both hemorrhage and shock states. Hemodialysis is used in kidney failure. (Hemodialysis involves mechanically cleansing the blood outside of the body, to replace the kidney's normal function of removing various toxins form the blood.) Rapid respiratory assistance is critical, often requiring intubation.

The anti-viral agent ribavirin has been approved for use in early treatment of hantavirus infections.

Prognosis

The diseases caused by hantaviruses are extraordinarily lethal. About 6-15% of people who contract HFRS have died. Almost half of all people who contract HPS will die. This gives HPS one of the highest fatality rates of any acute viral disease. It is essential that people living in areas where the hantaviruses exist seek quick medical treatment should they begin to develop an illness that might be due to a hantavirus.

Prevention

There are no immunizations currently available against any of the hantaviruses. In 2003, developments in genetic science were helping researchers work on a possible vaccination and therapy for several versions of hantavirus, including the Sin Nombre virus that causes HPS. With further work, a gene-based vaccine could become available in the future. However, the only known forms of hantavirus prevention involve rodent control within the community and within individual households. The following is a list of preventive measures:

• Avoiding areas known to be infested by rodents is essential.
• Keeping a clean home and keeping food in rodent-proof containers.
• Disposing of garbage and emptying pet food dishes at night.
• Setting rodent traps around baseboards and in tight places. Disposing of dead animals with gloves and disinfecting the area with bleach.
• Using rodenticide as necessary.
• Sealing any entry holes 0.25 inch wide or wider around foundations with screen, cement, or metal flashing.
• Clearing brush and junk from house foundations.
• Putting metal flashing around house foundations.
• Elevating hay, woodpiles, and refuse containers.
• Airing out all sealed outbuildings or cabins 30 minutes before cleaning for the season.
• When camping, avoiding sleeping on the bare ground. It is advised to sleep on a cot or in a tent with a floor.

Resources

BOOKS

Harper, David R., and Andrea S. Meyer. Of Mice, Men, and Microbes: Hantavirus. San Diego: Academic Press, 1999.

PERIODICALS

"DNA Vaccine Protects Against Hantavirus Pulmonary Syndrome." Heart Disease Weekly November 2, 2003: 31.

Jones, Amy. "Setting a Trap for Hantavirus." Nursing September 2000: 20.

Monroe, Martha C., Sergey P. Morzunov, Angela M. Johnson, Michael De. Bowen, et al. "Genetic Diversity and Distribution of Peromyscus-Borne Hantaviruses in North America." Nursing January-February 1999: 75-86.

Naughton, Laurie. "Hantavirus Infection in the United States: Are We Prepared?" Physician Assistant May 2000: 33.

Rhodes III, Luther V., Cinnia Huang, Angela J. Sanchez, Stuart T. Nichol, et al. "Hantavirus Pulmonary Syndrome Associated with Monongahela Virus, Pennsylvania." Emerging Infectious Diseases November 2000: 616.

Van Bevern, Pamela A. "Hantavirus Pulmonary Syndrome." Clinician Reviews July 2000: 108.

KEY TERMS

Hemodialysis— A method of mechanically cleansing the blood outside of the body, in order to remove various substances that would normally be cleared by the kidneys. Hemodialysis is used when an individual is in relative, or complete, kidney failure.

Hemorrhagic— A condition resulting in massive, difficult-to-control bleeding.

Petechiae— Pinpoint size red spots caused by hemorrhaging under the skin.

Platelets— Circulating blood cells that are crucial to the mechanism of clotting.

Prodrome— Early symptoms or warning signs

Pulmonary— Referring to the lungs.

Renal— Referring to the kidneys.

Shock— Shock is a state in which blood circulation is insufficient to deliver adequate oxygen to vital organs.

Hantavirus Infections

Hantavirus infections are the cause of two serious diseases, hantavirus pulmonary syndrome (HPS) and hemorrhagic fever with renal syndrome (HFRS). There are at least fourteen types of hantaviruses, which differ only slightly from one another, and scientists are working to identify and classify previously unrecognised hantaviruses. Well-known hantaviruses are are: Hantaan, Seoul, Puumala, Prospect Hill, Khabarovsk, Bayou, and Sin Nombre. The Sin Nombre virus was the cause of a 1993 outbreak in the southwestern United States, which led to a greater understanding of the virus and its transmission to humans.

The hantavirus are named for the Hantaan River in Korea. In 1976, a virus found near this river was shown to be the cause of a deadly disease, which was dubbed the Hantaan River disease. This same type of virus was likely responsible for a disease that appeared in United Nations troops stationed in Korea in 1951. Indeed, a 1990 study that examined serum that was collected and saved from Korean War (1950–1953) victims found that over 90% of the sera contained antibodies to hantavirus.

Until the early 1990s, reports of hantavirus infections were confined to the Far East and involved hemorrhagic fever and kidney failure. Then, in 1993, an illness outbreak occurred in the United States Southwest, where the states of Colorado, Arizona, New Mexico, and Utah meet (an area known as the Four Corners). A disease that initially appeared similar to the flu quickly progressed to a life-threatening illness within 24 hours to a few days. Lung function dramatically reduced as fluid accumulated in the lungs. Kidney failure also occurred in several victims. At least seven people died from the mysterious viral infections in the early stages of the Four Corners outbreak.

After state health departments and Indian Health Services in the Four Corners area tested the victims for all known disease agents, the Special Pathogens branch of the United States Centers for Disease Control (CDC) assisted with the intense public health investigation into the 1993 Four Corners outbreak. The cause of the outbreak was found to be a previously unrecognized hantavirus dubbed Sin Nombre virus (from Spanish, meaning no name ). The lung infection became known as hantavirus pulmonary syndrome. The virus was shown to live naturally in rodents, particularly the deer mouse. Mouse feces, urine, and saliva can contain the virus.

The 1993 outbreak is suspected to have arisen because of a period of heavy rain that occurred in the Four Corners region. The wet conditions produced an explosion in the deer mouse population. The virus could then be spread from mice to humans more easily.

Dusty environments are particularly important in the spread of hantavirus. The virus particles left behind upon the drying of feces or saliva can be distributed into the air and inhaled into the lungs.

Hantavirus pulmonary syndrome has also occurred in South America. Indeed, it is more common in South America than in North America. Additionally, the hantavirus types found in North and South America cause a more serious disease than many of the hantavirus types that are found in the Far East.

Treatment of hantavirus pulmonary syndrome is mostly supportive and can be difficult. The condition of a person with HPS often deteriorates so rapidly that

KEY TERMS

Hantavirus —A virus carried by rodents, especially the deer mouse, that is responsible for the disease hantavirus pulmonary syndrome.

Hantavirus pulmonary syndrome —A serious febrile illness associated with respiratory compromise or failure and caused by a hantavirus that is usually transmitted through inhalation of aerosolized rodent droppings.

Hemodialysis —A method of mechanically cleansing the blood outside of the body, used when an individual is in relative or complete kidney failure, in order to remove various substances which would normally be cleared by the kidneys.

Outbreak —The appearance of new cases of a disease in numbers greater than the established incidence rate, or the appearance of even one case of an emergent or rare disease in an area.

diagnosis and hospitalization must occur very quickly. Treatment mainly consists of clearing fluid from the lungs to preserve lung function, maintaining blood pressure and, if necessary, initiating kidney dialysis (hemodialysis) and mechanical ventilation. Anti-viral medications are more effective for treating the HFRS version of hantavirus infection than HPS. For those who survive, recovery is almost as rapid as was the progression of the infection.

For the present time, the best defense against hantavirus is to avoid environments where exposure to rodents and their droppings could occur. People should particularly avoid entering or cleaning rodent-infested structures, such as old barns or storage sheds.

See also Physiology; Respiratory diseases; Zoonoses.

Resources

BOOKS

Harper, David S., and Meyer, Andrea S. Of Mice, Men, and Microbes: Hantavirus. Burlington, MA: Academic Press, 2000.

PERIODICALS

Glass, G. E., J.E. Cheek, J.A. Patz, et al. “Using Remotely Sensed Data to Identify Areas at Risk for Hantavirus Pulmonary Syndrome.“Emerging Infectious Diseases 6 (March-April 2000): 238–247.

Kreeger, K.Y. “Stalking the Deadly Hantavirus: A Study in Teamwork.” The Scientist 8 (July 1994): 1–4.

OTHER

Centers for Disease Control and Prevention. “Tracking a Mystery Disease: The Detailed Story of Hantavirus Pulmonary Syndrome.” <http://www.cdc.gov/ncidod/diseases/hanta/hps/noframes/outbreak.htm> (accessed November 26, 2006).

Brian Hoyle

Hantavirus Pulmonary Syndrome

What is Hantavirus Pulmonary Syndrome?

Is HPS Common?

What Are the Symptoms of HPS?

How Do Doctors Diagnose HPS?

How Is HPS Treated?

Can HPS Be Prevented?

Resources

Hantavirus pulmonary syndrome (HAN-tuh-vy-rus PUL-mo-nar-ee SIN-drome) is a lung disease that causes respiratory distress (breathing difficulty) and, in some cases, death. Hantavirus, the virus that causes the disease, is carried by rodents.

KEYWORDS

for searching the Internet and other reference sources

Hantavirus

Pulmonary system

Sin Nombre virus

Viral zoonoses

What is Hantavirus Pulmonary Syndrome?

Hantavirus pulmonary syndrome, or HPS, is a potentially deadly disease that attacks the lungs. A family of viruses called hantavirus causes HPS. These viruses live in rodents but do not make them sick. The Sin Nombre virus (SNV) hantavirus causes most HPS in the United States, but some cases have come from the Bayou, the New York, and the Black Creek Canal viruses.

Camp with Care

The great outdoors is home for most rodents, and many of them carry hantavirus. Campers can help keep camping and hiking trips safe by following a few simple precautions:

• using a tent with a built-in floor and pitching it away from woodpiles or any rodent nests or burrows
• sleeping on a raised surface, at least 12 inches off the floor
• airing out cabins that have not been used for a half hour or more, then checking for rodent droppings
• using water and disinfectant to wipe out the area (no sweeping!)
• keeping all food in rodent-proof containers
• burying or burning trash
• using bottled water for drinking, cooking, and all washing
• staying away from mice, rats, chipmunks, and all other rodents.

Rodents, usually mice and rats, shed hantavirus in their saliva, urine, and droppings. Humans catch the virus when they disturb dried droppings (by sweeping, for example) and inhale the particles that are sent into the air. People can also contract hantavirus by touching an infected animal or its droppings and then touching their nose or mouth. Eating food or drinking water contaminated by rodent droppings is another source of infection. Rodent bites, although rare, can also spread the disease.

The most common carriers of hantavirus are deer mice (found almost everywhere in North America), cotton rats and rice rats (found in the southeastern United States and Central and South America), and white-footed mice (found in most parts of the United States and Mexico). Cats and dogs do not carry hantavirus and they cannot catch it from rodents. However, cats and dogs can spread hantavirus to humans if they bring an infected rodent into a home or other buildings where people live or work.

Is HPS Common?

HPS is rare. Health authorities first recognized the disease in the United States in 1993, and the U.S. Centers for Disease Control and Prevention (CDC) recorded only 333 reported cases through early 2003. Although HPS occurs in people throughout North and South America, most cases in the United States appear in the Southwest and in places that are infested with rodents.

People of every age, sex, and race can contract HPS, but it is not contagious and cannot be spread by sneezing, coughing, kissing, or having other bodily contact.

What Are the Symptoms of HPS?

The first symptoms of HPS usually appear 1 to 5 weeks after a person has been exposed to the virus. HPS can be difficult to diagnose because the early signs, such as fever, tiredness, and body aches, are similar to those of the flu. About half of the people who catch HPS also may experience dizziness, chills, nausea, vomiting, abdominal* pain, or headaches.

*abdominal

(ab-DAH-mih-nul) refers to the area of the body below the ribs and above the hips that contains the stomach, intestines, and other organs.

From 2 to 5 days after the first symptoms, a person infected with hantavirus starts coughing and experiences shortness of breath. The disease quickly becomes more severe, and people who do not receive immediate treatment may become extremely ill and go into shock*, needing intensive care in a hospital.

*shock

is a serious condition in which blood pressure is very low and not enough blood flows to the body’s organs and tissues. Untreated, shock may result in death.

How Do Doctors Diagnose HPS?

A doctor may suspect HPS if a person with flulike symptoms complains about difficulty breathing, especially if the person has been exposed to rodents or rodent droppings. To confirm the diagnosis, the doctor uses blood tests to see if the person has developed antibodies* to a strain* of hantavirus. Chest X rays or ultrasound* images can help the doctor check the condition of a person’s heart and lungs.

*antibodies

(AN-tih-bah-deez) are protein molecules produced by the body’s immune system to help fight specific infections caused by microorganisms, such as bacteria and viruses.

*strains

are various subtypes of organisms, such as viruses or bacteria.

*ultrasound ,

also called a sonogram, is a diagnostic test in which sound waves passing through the body create images on a computer screen.

How Is HPS Treated?

HPS is a serious disease, and someone who has it needs treatment in a hospital’s intensive care unit. There he might be given fluids, have his blood pressure monitored, and have a tube inserted in his throat to help him breathe. Because a virus causes HPS, antibiotics do not work against it, although an antiviral drug may help some patients. According to the CDC, 38 percent of reported cases of HPS have been fatal.

Doctors today know more about the disease and are quicker to get patients into treatment. The earlier people with HPS receive help, the better their chances of survival. Recovery from HPS is fairly fast, although patients may feel worn out for several months.

Can HPS Be Prevented?

There is no vaccination available for HPS. The best way to avoid contracting the virus is to get rid of possible sources of infection, which means avoiding woodpiles and other places where rodents live outdoors and keeping homes and workplaces free of mice and rats. Experts also recommend sealing holes where rodents can enter (they can squeeze through spaces as small as .25 inch in diameter) and wearing a mask and gloves when cleaning out areas with rodent droppings.

See also

Public Health

Zoonoses

Resources

Organization

National Center for Infectious Diseases, U.S. Centers for Disease Control and Prevention, Mailstop C-14, 1600 Clifton Road, Atlanta, GA 30333. The website for this government agency provides an extensive look at HPS, including advice on preventing the disease.

Telephone 800-311-3435 http://www.cdc.gov/ncidod

Website

Discovery Online. Death in the Desert. This article, which can be found through the site’s Plague Patrol page, describes how researchers found hantavirus in the American Southwest in 1993, solving several mysterious deaths.

http://www.discovery.com/stories/science/infectious/infectious.html

HANTAVIRUS INFECTIONS

DEFINITION

Hantavirus infections are caused by a group of viruses known as hantaviruses. These viruses cause two serious illnesses in humans. They are hemorrhagic (pronounced heh-meh-RA-jik) fever with renal syndrome (HFRS) and hantavirus pulmonary syndrome (HPS).

DESCRIPTION

Hantaviruses live in rodents, such as rats and mice, without causing any symptoms. The viruses can be transmitted (passed on to) humans by way of urine, feces, or saliva from the rodents. Five different kinds of hantaviruses have been discovered so far. Each is found in a different geographical region and in different kinds of rodents. As an example, the virus known as the hantaan virus is carried by the striped field mouse. It is found primarily in Korea, China, East Russia, and the Balkans. This virus causes HFRS. Another type of hantavirus is called the Sin Nombre virus. It is carried by the deer mouse and found primarily in southwestern United States and causes severe cases of HPS.

SYMPTOMS

The two forms of hantavirus infections each have distinctive symptoms.

Hemorrhagic Fever with Renal Syndrome (HFRS)

The three most common symptoms of HFRS are mentioned in the name of the disease. The first of those symptoms is a fever. The second symptom is malfunction of the kidneys. The term renal means "relating to the kidneys." The third symptom is a low platelet count. Platelets are blood cells that promote the clotting of blood. When the number of platelets in blood is reduced, blood clotting does not occur properly. A person tends to hemorrhage (pronounced hem-ir-idj) or bleed easily.

Patients with HFRS have pain in the head, stomach, and lower back. They may also have bloodshot eyes and blurry vision. Hemorrhaging may occur through tiny openings on the upper body and in the mouth. The patient's face, chest, abdomen, and back often appear bright red, as if sunburned.

Five days into the disease, the patient may experience a sudden drop in blood pressure. He or she may go into shock. Shock occurs when the heart does not pump enough blood through the veins and arteries. Cells do not get blood and the needed oxygen it carries. Shock can cause damage to the body's organs, especially the brain.

After about eight days, kidney damage may taken place. The kidneys are responsible for filtering toxins (poisons) out of the blood. If the kidneys do not function properly, those toxins can damage cells throughout the body. Hemorrhaging may also become more serious throughout the body. Blood may begin to appear in the urine or when a person vomits. Hemorrhaging in the brain can cause the most serious problems that can include a loss of consciousness.

These symptoms can become even more serious about eleven days into the infection. A person may become very confused, begin to have hallucinations, and go into seizures. A person who hallucinates sees and hears things that are not really there. Problems can also develop with the lungs and the ability to breathe normally.

At this point, the patient faces a turning point. He or she may continue to become more and more ill, with death as the result. Or the infection may begin to clear up. In the latter case, full recovery may take up to six weeks.

Hantavirus Infections: Words to Know

Hemodialysis:

A mechanical method for cleansing blood outside the body.

Hemorrhagic:

Relating to a condition in which there is massive, difficult-to-control bleeding.

Platelets:

Blood cells that have a role in the process of blood clotting.

Pulmonary:

Relating to the lungs.

Renal:

Relating to the kidneys.

Shock:

A condition in which blood pressure drops suddenly and the flow of blood to cells is dramatically reduced. Because of this reduced flow, cells are not able to get the oxygen they need.

Hantavirus Pulmonary Syndrome (HPS)

The first symptoms of HPS are fever and a sudden drop in blood pressure. These symptoms may be followed by shock and loss of blood in the lungs. When this happens, fluids may collect in the lungs, leading to shortness of breath. These symptoms can occur so quickly that the patient goes into respiratory failure in a matter of hours. Respiratory failure means that the patient has lost the ability to breathe on his or her own.

Blood tests are used to diagnose hantavirus infections. Blood taken from a patient is analyzed for the presence of certain hantavirus antibodies. Antibodies are substances produced by the blood when it has been infected by a foreign body, such as a bacterium or a virus. Antibodies are very specific. That is, a particular kind of antibody is produced to fight every different kind of infective agent (bacterium, fungus, virus, etc.). An analysis of a person's blood can tell whether he or she has been infected with a hantavirus and, if so, by what kind of hantavirus.

There is no way to kill the hantavirus. Treatments for hantavirus infections are designed, therefore, to relieve the symptoms of the disease. For example,

a person who has been hemorrhaging or who is in shock may require blood transfusions. Hemodialysis (pronounced HEE-mo-die-ali-sis) is used to remove toxins from the blood of a person whose kidneys have failed. Hemodialysis is a procedure by which a person's blood is passed through a machine to take out dangerous toxins (replacing the function of the kidneys).

Hantavirus infections progress very rapidly. It is important, therefore, to begin treatment as quickly as possible and to observe the patient very carefully.

An experimental drug being tested on hantavirus infections is called ribavirin (pronounced RI-buh-vih-rin). The drug has been shown to kill the hantavirus in laboratory tests. It is too soon to tell how well it will work in human beings.

Hantavirus infections are very lethal (capable of causing death). About 6 to 15 percent of those who develop HFRS will die of the disease. The death

rate for those who contract (catch) HPS is about 50 percent. These numbers point out how important it is for people with symptoms of hantavirus infections to get treatment as quickly as possible.

There is no way to prevent a hantavirus infection. The best way to avoid getting the disease is to reduce one's exposure to the rodents that carry the virus. That means keeping one's living quarters as clean as possible.

FOR MORE INFORMATION

Books

Cockrum, E. Lendell. Rabies, Lyme Disease, Hanta Virus: And Other Animal-Borne Human Diseases in the United States and Canada. Tucson, AZ: Fisher Books, 1997.

Harper, David R. and Andrea S. Meyer. Of Mice, Men, and Microbes; Hantavirus. New York: Academic Press Inc., 1999.

Stoffman, Phyllis. The Family Guide to Preventing and Treating 100 Infectious Diseases. New York: John Wiley & Sons, 1995.

Periodicals

"Outbreak of Hantavirus Is Unusual." The New York Times (June 17, 1997): pp. C4+.