Picture courtesy of tell.fll.purdue.edu/JapanProj/FLClipart/Medical.

Syndromes and Symptoms

There are 51 known immunologically distinct serotypes of adenovirus that can infect humans. Despite the similarities among genomic and virion organization of adenoviruses they are unique in both their routes of transmission and their tissue tropism. Therefore there is little cross-reactivity between them, so that a given individual can be infected with adenovirus multiple times throughout his/her lifetime.

Adenoviruses are often asymptomatic and rarely fatal. However they do tend to cause more severe respiratory disease than enteroviruses and they can persist in the human host for long periods of time, and they can cause severe complications in immunocompromised people.

The type of disease caused by adenoviruses depends largely on the route of transmission and the tissue tropism of the particular strain

Examples:

Acute Respiratory Disease (4, 7, 14, 21):

• Incubation: 3 weeks
• Epidemiology: Most common among military recruits, especially newly enlisted troops, but rare among healthy civilian adults. Potential explanations for this include crowded living quarters among troops (and therefore frequent exposure to infected individuals) and frequent, vigorous exercise. Acute Respiratory disease is most common in the winter.
• Symptoms and Outcome: Symptoms include fever, malaise, sore throat, hoarseness, cough, and pneumonia (10% of cases). Infection is generally not severe and will resolve in 2-4 days (fever) or 10-14 days (complete recovery). Although there is low mortality associated with acute respiratory disease, up to 25% of infected military recruits require short-term hospitalization for fever and infections in the lower respiratory tract.
• Prevention and Management: A vaccine consisting of a capsule of non-attenuated adenoviruses 4 and 7 was used among military recruits from 1971-1996. Because the virus was injected, rather than inhaled, it caused asymptomatic infections in the gut, thereby stimulating an immune response, rather than causing active infections in the respiratory tract. Thus this vaccine was attenuated by the route of transmission. The vaccine has not been made since 1996, so general symptomatic treatment is normally provided. As with all respiratory transmitted adenoviruses, adenoviruses 4, 7, 14, and 21 can be prevented through diligent hand washing and other personal hygiene, isolation of patients, overall sanitation of the living quarters, and by minimizing the amount of crowding and stress in the recruits lifestyle.

Epidemic Keratoconjunctivitis (8, 19, 37):

•Incubation: 2-14 days, although the person may be infectious for 10-14 days after the onset of symptoms.

• Epidemiology: As its name suggests, epidemic keratoconjunctivitis generally occurs in local outbreaks (such as schools, hospitals, eye clinics, camps, nursing homes, or workplaces.) The disease has been documented in Asia (especially Japan) for many years but was not generally found in the United States until an outbreak of 10,000 cases reported in the shipyards of Pearl Harbor in 1941. Epidemic keratoconjunctivitis occurs more frequently in adults than children; men and women are generally infected equally.
• Symptoms and Outcome: Epidemic keratoconjunctivitis tends to have a sudden onset. Symptoms include eye redness and chemosis followed by periorbital swelling, pain, photophobia, preauricular lymphadenopathy, punctuate keritis, and superficial corneal opacities. Most symptoms resolve in 4-6 weeks although corneal opacities may last for years and may cause permanent visual impairment. There is very low mortality associated with epidemic keratoconjunctivitis.
• Prevention and Management: There is no vaccine for epidemic keratoconjunctivitis, so management is normally limited to soothing the infected eye (hot compresses, etc.) or other symptomatic treatments. Since epidemic keratoconjunctivitis is spread through direct contact with contaminated surfaces, followed by autoinoculation of the eye, simple hygienic measures, such as hand washing or glove wearing and sterilization of contaminated surfaces.

Others:

• Pneumonia (1, 2, 3, 7)
• Pharyngitis (1, 2, 3, 5, 7)
• Pharyngoconjunctival fever (3, 7)
• Follicular conjunctivitis (3, 4, 11)
• Petussis-like syndrome (5)
• Acute infantile gastroenteritis (40, 41)
• Intususseption (1, 2, 5)
• Meningitis (3, 7)
• Other severe disease in immunocompromised people (5, 34, 35)

The severity of disease caused by adenoviruses also depends on the age and immune status of the infected individual, although a variety of other social and physical factors may also cause more severe disease. Examples of immunocompromised people include premature babies/neonates, transplant recipients, cancer patients, or those suffering from HIV/AIDS or a genetic disorder such as SCIDS. Severe and potentially deadly infections in immunocompromised people include pneumonia, hepatitis, encephalitis, nephritis, and gastroenteritis. Up to 50% of SCIDS patients die of complications associated with adenovirus infection.