Viruses

Definition

Viruses are not living things but tiny protein-covered parcels of genetic material (either DNA or RNA) that become active only in the cells of living organisms such as the human body. Viruses are not active in the air or on surfaces. Within a human cell or other host cell, a virus releases its DNA or RNA and infects the cell, then reproduces and spreads rapidly to nearby cells resulting in viral infection.

Description

The only purpose viruses have is to reproduce, which depends on taking over a living organism and inserting their genetic material into its cells. Unlike bacteria, which are living organisms that consume and metabolize nutrients, reproduce, and adapt to their environment, viruses are not organisms and, on their own, do not absorb or metabolize nutrients, move around or reproduce unless they are within the cells of a living organism. Once inside living cells of a host, they use the normal functions of the host cells to carry out instructions programmed in their own viral DNA or RNA, including reproducing themselves and occupying the living organism. Although viruses often infect more than one type of organism, including plants, animals, birds and humans, reactions to the virus by each organism are usually different—it may be harmless in one, while infecting and killing another. Viruses infect different parts of the body and the same virus may also affect different people in different ways, depending on the status of their general health and their immune system .

Many viruses infect humans, including: viruses that cause common diseases of childhood such as measles (rubella virus) and chicken pox (herpes zoster virus) among others; viruses that cause the common cold , respiratory infections (e.g., influenza or flu, respiratory syncytial virus, parainfluenza, rhinovirus, and coronavirus), stomach virus (not the same virus that causes influenza or “flu”), shingles (herpes zoster virus), and certain types of sexually-transmitted diseases (e.g., human papilloma virus and genital herpes). HIV (human immunodeficiency virus) is an aggressive virus that has affected the immune system of susceptible individuals worldwide. Senior adults who have chronic disease of any kind (e.g., heart, lung or liver disease and diabetes) or whose immune system is weakened (immunodeficiency) may not able to respond to viruses by developing antibodies against them, placing them at higher risk than younger adults of becoming seriously ill or developing complications from certain common viruses.

Viruses Common in Senior Adults

• Influenza virus (flu)is an acute respiratory infection that is highly contagious with possible life-threatening complications in elderly and immunocompromised adults. It is spread by airborne droplets of virus-containing fluids sneezed or coughed into the atmosphere from the nose and throat of infected individuals. Bacterial infection may follow influenza, leading to pneumonia. Influenza viruses are classified as A, B or C, according to prevalence and the presence of complications. Influenza virus A is most prevalent with greatest likelihood of serious complications such as pneumonia, and has been associated with major epidemics; B is a milder virus and rarely occurs in epidemic proportions; C does not cause typical influenza and has never caused epidemics. An increase in deaths from influenza has been noted since the 1990s due to the aging population. Avian influenza (bird flu) is caused by a strain of influenza A that typically infects wild birds, but has only rarely been detected in humans, usually related to direct contact with an infected bird and never in western countries of the world.
• Common cold virus is a relatively minor viral infection of the upper respiratory tract, including nose and throat. Colds are especially contagious, spreading rapidly between individuals when fluid containing the cold virus is passed from one person to another, either by touch or by inhaling fluid droplets from sneezes and coughs. Adults who catch cold frequently, or have colds that last more than two weeks, may have immune system deficiencies that should be investigated.
• Hepatitis C virus causes inflammation of the liver. Hepatitis C virus (HCV) is acquired from direct contact with the blood of someone who has HCV), either through blood transfusions or blood-contaminated needles. It is not believed to be acquired by casual or sexual contact. At highest risk for infection by hepatitis C are people who received blood transfusions before 1992 when U.S. law began to require all donors, units of blood and blood components to be tested for hepatitis C. Older adults are at high risk because hepatitis C virus can be present in the body for years without producing symptoms and can become chronic before symptoms develop, leading gradually to permanent liver damage, cirrhosis and liver failure.(See Hepatitis.)
• Respiratory Syncytial Virus (RSV) is a common contagious virus among children during the winter season but has also been shown through research in 2003 to be as great a threat to senior adults and those with chronic disease as influenza A. Among approximately 177,500 elderly adults hospitalized each year with flu-like symptoms or related pneumonia, 90% are diagnosed with influenza virus and 78% with RSV infection.
• Herpes zoster virus (Shingles) is a nerve infection caused by the same virus (varicella zoster virus) that causes chickenpox, which becomes reactivated either by stress (not “nervousness”), presence of another illness such as cancer, or a weakened immune system. It develops as a red, blotchy rash on the chest, legs, or another part of the body. Because it is a nerve disorder, pain can be the predominant symptom. It is not related to genital herpes or herpes mouth sores.

Demographics

Elder adults, especially those with chronic disease or immune system dysfunction, are at high risk of infections caused by respiratory viruses such as influenza viruses A and B and respiratory syncytial virus (RSV); 35,000 individuals a year die from influenza A alone and as many as 69,000 individuals in an epidemic year. Each year about 14,000 seniors and other high-risk adults die of RSV. Viruses are identified in 0.3 to 30% of cases of community-acquired pneumonia and 50% are over age 60. Up to 40% of all viral hepatitis cases are hepatitis C occurring in adults age 50 or older. The U.S. Center for Disease Control (CDC) reports that four million people are infected with hepatitis C virus and 2.7 million have chronic infection. Shingles (herpes zoster) can affect anyone who has had chickenpox, but occurs most frequently in senior adults over age 60, resulting in over 500,000 cases each year in the United States.

Causes and symptoms

All virus infections are caused by the presence of a specific virus in the cells of the body. Most respiratory viruses and hepatitis C are spread by direct contact with individuals who already have the virus or contact with their body fluids which contain virus-infected cells. Herpes zoster is caused by reactivation of the chickenpox virus in a period of illness or stress .

The common symptoms of influenza virus are fever and chills, headache, body aches and pains, weakness, sore throat and nasal congestion, dry cough, and loss of appetite. Some individuals may have difficulty breathing, reduced levels of oxygen or chest noises (rales or wheezing). Symptoms of RSV are similar to symptoms of a bad cold at first, but commonly progresses to bronchiolitis and pneumonia in older individuals with chronic disease or immunodeficiency. The common cold will begin with nose and throat symptoms, including congestion and mucus production, but is seldom accompanied by fever, with symptoms clearing in a week or two.

Stomach flu symptoms include nausea, vomiting and diarrhea for a 24-hour period. Stomach flu virus is not related to the influenza virus that causes respiratory illness.

People with chronic hepatitis C may have no symptoms at all for years, but typical flu-like symptoms or skin rashes can appear suddenly. Characteristic symptoms of hepatitis are similar to flu symptoms, including fever, fatigue, weakness, nausea, vomiting, loss of appetite, abdominal disturbances, diarrhea and aching muscles and joints. Yellowing of the skin, eyes and urine may also occur in some individuals.

Shingles has a characteristic red, blotchy rash with eventual blister-like sores. It is accompanied by intense pain as the virus moves along affected nerves to get to the skin surface.

Diagnosis

Physicians diagnose viruses such as influenza or RSV by comparing the affected individual's symptoms to specific symptoms prevalent in the community where the viral infection has spread. Laboratory tests are seldom used, however chest x-rays may be taken to detect possible pneumonia in individuals with influenza-like symptoms. Cell cultures can be done to identify influenza; however, because this type of testing is slow to produce definitive results, it is not often used except to confirm the identity of the virus causing a community-wide infection. Tests for antibodies against RSV found in human serum are available and often performed to distinguish RSV from influenza A. Hepatitis C virus can be identified in the laboratory and a home testing kit is also available to detect presence of the virus even before symptoms appear. Herpes zoster or shingles is diagnosed by the presence of characteristic sores and associated pain.

Treatment

Viruses are difficult to treat because they adapt within host cells and change their DNA/RNA characteristics (gene mutation) before they attack other individuals, always developing new strains so their activity can not be effectively stopped by antibodies developed from prior virus infections. Antibiotics are not prescribed for viruses because they only act against bacteria; however, bacterial infections such as pneumonia that result from virus infections will be treated with antibiotics. Typical treatment for influenza is to let it run its course; doctors advise staying in bed, drinking plenty of fluids and taking aspirin or acetominophen to relieve fever and body aches. Vaccines are available against certain viruses, including influenza type A, which is recommended by most physicians for senior adults or individuals with compromised immune function. No vaccine is yet available for RSV but it is a high priority among researchers. Some adults with RSV may need oxygen therapy , and severe disease in immunocompromised patients may be treated with intravenous immune globulin (IGIV) containing RSV-neutralizing antibodies.

QUESTIONS TO ASK YOUR DOCTOR

• Is my condition caused by a virus? Which virus?
• What can I do to recover?
• How can I avoid viruses?
• Am I at greater than average risk for viral infection? Why?

Antiviral drugs approved by the FDA are available but are not prescribed routinely for influenza and other common viruses. Antiviral drugs such as amantadine and rimantadine, which reduce penetration of cells by the virus, may be used in high-risk individuals but resistance develops quickly, making the drugs ineffective. The main clinical benefit of antiviral drugs is slight reduction of symptom duration.

Hepatitis C is treated with bed rest, nutritious food, drinking a lot of water to flush the body and avoiding alcohol or medications that may affect the liver. Oral anti-viral drugs may be given to some individuals. Recovery can be successful although individuals compromised by another chronic disease or a weakened immune system may develop chronic hepatitis C infection and complications leading to cirrhosis and liver failure.

The skin rash of shingles is sometimes treated with acyclovir or cortisone taken orally to treat underlying nerve inflammation. Over-the-counter pain killers such as acetaminophen may be taken and sometimes stronger pain medications will be prescribed. Patients are advised not to use skin medications or to open the sores; white vinegar in warm water is recommended for gently washing affected areas. When skin eruptions clear up and pain persists, a cream (Zostrix) can be used on painful areas.

Nutrition/Dietetic concerns

Natural, antiviral neutraceuticals and immune system boosters are available that can shorten duration and severity of viral illness, including:

• DHEA, an adrenal hormone with antiviral and immune-boosting benefits.
• Melatonin, a pineal hormone shown to enhance immune system function.
• Sambucol, black elderberry extract shown in studies to have antiviral activity aginst strains of influenza virus.
• Lactoferrin, a component of whey (non-fat portion of milk) shown to have antiviral, antimicrobial effects as well as ability to enhance immune function.
• Echinacea, known for its immune system boosting properties.
• Garlic, with active component allicin, offers antifungal, antibacterial and antiviral activity with beneficial effects on immune system function.

Prognosis

Most people recover fully from influenza or other respiratory viruses within one to two weeks but viral respiratory illness and related pneumonia can result in serious complications and death in high-risk older adults with chronic disease or immune system dysfunction. Viral infections may develop more easily in individuals who do not have full immune response to fight the causative virus. Lack of immune response by the individual may lead to systemic infection, sepsis and death.

Some individuals who have the hepatitis C virus from prior transfusion never develop liver inflammation. Other individuals may develop chronic hepatitis C and progressive liver disease that may lead to cirrhosis, liver failure, transplantation or death.

Most individuals recover within several weeks from the skin eruptions of shingles with no serious consequences. However, pain can continue for up to six months because nerves heal extremely slowly.

Prevention

Annual vaccination against influenza virus is recommended for high-risk groups such as senior adults over age 65, people with chronic disease and reduced immune system function. Researchers and physicians, however, vary in their opinions about the effectiveness of vaccines as protection against influenza virus in vulnerable populations. Individuals should depend on the advice of their own physician. No vaccine is yet available for RSV infection.

Washing hands is still an important preventive method against airborne viruses. Although viruses don't live long on surfaces, nose and throat secretions from infected people contain virus-infected cells that can live for up to 24 hours on door knobs, toilet seats, glassware, telephones, cell phones and other surfaces. Touching the live virus and then placing fingers in the mouth or nose can transmit the viral disease. Infectious disease experts say that washing hands frequently can help prevent acquiring respiratory viral infection such as influenza and RSV.

KEY TERMS

DNA —An important genetic determinant, deoxyribonucleic acid (DNA) is found in nuclei of human and plant cells, functioning as the reproducing component of chromosomes, controlling hereditary characteristics; also present in viruses.

genetics —The science of biologic inheritance and the transmission of traits of a single organism through possession of specific genes, which are the units of heredity.

gene mutation —Changes in a gene that may change the way it expresses inherited traits in an organism.

immunodeficiency —Describing the lack of basic functioning of the immune system designed to ward off disease.

RNA —An important genetic determinant, ribonucleic acid (RNA) is found in nuclei of human and plant cells and functions as a reproducing component of chromosomes, controlling hereditary characteristics; also present in viruses.

Individuals at greater risk for infection should obtain good nutrition with fresh, whole foods, regular sleep and regular exercise to help their immune systems generate cells needed for immune response. Besides practicing good hygiene, individuals with known immune deficiency must reduce the threat of viral infection by avoiding crowds and contact with friends, family members or others who have viral infections, including colds, flu and other viral respiratory infections.

Caregiver concerns

Caregivers should protect themselves and others in the household while caring for senior adults with contagious viral infection, including washing hands frequently, wearing a protective face mask, and obtaining vaccination if available.

Individuals with chronic disease or whose immune system functioning is reduced should be protected from exposure to viral infection by avoiding crowds and contact with other individuals who may have viral infections, particularly influenza or respiratory infections. Good hygiene should be practiced, including frequent and thorough hand washing.

Resources

BOOKS

“Influenza.” The Merck Manual of Diagnosis and Therapy, Section 14. R.S. Porter, ed. White House Station, NJ: Merck Research Laboratories, 2007.

“Chronic Hepatitis.” The Merck Manual of Diagnosis and Therapy, Section 16. R.S. Porter, ed. White House Station, NJ: Merck Research Laboratories, 2007.

“Influenza virus.” Disease Prevention and Treatment. Expanded 4th ed. M. Segala, Ed. Ft. Lauderdale, FL: Life Extension Foundation; 2003, 1049–1054.

PERIODICALS

Thompson WW, Shay DK, Weintraub E et al. “Mortality Associated with Influenza and Respiratory Syncytial Virus in the United States.” Journal of the American Medical Association. 289(2); 2003.

Falsey A. “Community-Acquired Viral Pneumonia.” Clinics in Geriatric Medicine 23(3); 2007.

OTHER

“Respiratory Syncytial Virus May Kill as Many Elderly as Flu.” Senior Journal: Senior Citizens Information and News. Seniorjournal.com, 2003. Available at www.seniorjournal.com/NEWS/Health/6-01-13-Respirator-ySyncytialVirus.htm. Accessed March 16, 2008.

“Respiratory Syncytial Virus.” Centers for Disease Control and Prevention. Available at www.cdc.gov/ncidod/dvrd/revb/respiratory/rsvfeat.htm. Updated Jan. 2005. Accessed March 17, 2008.

Hecht F. “Shingles (Herpes Zoster).” Medicine Net. Updated March 7, 2008. Available at www.medicinenet.com/. Accessed March 17, 2008.

ORGANIZATIONS

National Institute of Allergy and Infectious Diseases (NIAID), 6610 Rockledge Drive MSC 6612, Bethesda, MD, 301-496-5717, 866-284-4107, 301-402-3573, www3.niaid.nih.gov.

L. Lee Culvert