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Adenovirus infections

Adenoviruses are a class of DNA viruses (small infectious agents) that can cause upper respiratory tract infections, conjunctivitis, and other infectionsin humans. Infants and children are most commonly affected by adenoviruses. Adenovirus infections can occur throughout the year, but seem to be most common from fall to spring.

Adenoviruses are responsible for 3-5% of acute respiratory infections in children and 2% of respiratory illnesses in civilian adults. They are more apt tocause infection among people who live in close contact. Outbreaks among children are frequently reported at boarding schools and summer camps. Most children have been infected by at least one adenovirus by the time they reach school age. Most adults have acquired immunity to many adenoviruses due to infections they had as children.

An adenovirus infection can either be acute or chronic. In acute infections,adenoviruses use healthy cells in the body to replicate up to one million newviruses per cell. Once the new viruses are produced, the infected cell bursts open and releases them. People with this kind of infection feel sick. In chronic or latent infection, a much smaller number of viruses are released andhealthy cells can multiply more rapidly than they are destroyed. People who have this kind of infection don't feel sick.

In children, adenoviruses most often cause acute upper respiratory infectionswith fever and runny nose. Occasionally more serious lower respiratory diseases, such as pneumonia, may occur.

Adenoviruses also cause acute pharyngoconjunctival fever in children. Symptoms, which appear suddenly, usually disappear in less than a week. The symptomsinclude inflammation of the lining of the eyelid (conjunctivitis), fever, sore throat, runny nose, and swollen lymph glands in the neck.

Other adenoviruses also cause fever and acute diarrhea in young children. This condition can last as long as two weeks. Another type of adenovirus can cause hemorrhagic cystitis (inflammation of the bladder and of the tubes that carry urine to the bladder from the kidneys). A child who has hemorrhagic cystitis has bloody urine for about three days, and invisible traces of blood canbe found in the urine a few days longer. The child will feel the urge to urinate frequently, but will have difficulty doing so, for about the same lengthof time.

In adults, the most frequently reported adenovirus infection is acute respiratory disease. This disease often strikes military recruits. Symptoms includefever, sore throat, runny nose, and cough. Other symptoms that may appear areweakness, chills, headache, and swollen lymph glands in the neck. The symptoms typically last three to five days.

Another illness caused by an adenovirus is epidemic keratoconjunctivitis. This inflammation of tissues lining the eyelid and covering the front of the eyeball can be caused by using contaminated contact lens solutions or by dryingthe hands or face with a towel used by someone who has this infection. The inflamed, sticky eyelids characteristic of conjunctivitis develop 4-24 days after exposure and last between one and four weeks. Only 5-8% of patients with epidemic keratoconjunctivitis experience respiratory symptoms. One or both eyes may be affected. As symptoms of conjunctivitis subside, eye pain and watering and blurred vision develop. These symptoms of keratitis may last for several months, and about 10% of these infections spread to at least one other member of the patient's household.

Specific adenovirus infections can be traced to particular sources and produce distinctive symptoms. In general, however, adenovirus infection is caused by:

Although symptoms may suggest the presence of adenovirus, distinguishing these infections from other viruses can be difficult. A definitive diagnosis is based on culture or detection of the virus in eye secretions, sputum, urine, or stool.

Treatment of adenovirus infections is usually aimed at relieving symptoms. Bed rest may be recommended along with medications to reduce fever and/or pain.(Aspirin should not be given to children because of concerns about Reye's syndrome.) Eye infections may benefit from topical corticosteroids to relieve symptoms and shorten the course of the disease. Hospitalization may be required for certain severe infections. No effective antiviral drugs have been developed.

Adenovirus infections are rarely fatal and most patients recover fully. Practicing good personal hygiene and avoiding people with infectious illnesses canreduce the risk of developing adenovirus infection. Proper handwashing can prevent the spread of the virus by oral-fecal transmission. Sterilization of instruments and solutions used in the eye can prevent eye infections, as can adequate chlorination of swimming pools.