Adenoviruses were ﬁrst isolated from adenoid tissue from ton- sillectomies of children and from military patients with febrile illness (1953). There are more than 49 human serotypes, sev- eral of which have oncogenic potential. The virus can become latent in lymphoid tissue and reactivated at a later date. Reac- tivation occurs during immunosuppression but it is unclear how long the virus persists (220,221).
Adenoviruses can cause acute respiratory illness, includ- ing pneumonia in military recruits or groups of infants. Most people have been infected with one serotype of adenovirus by age 15. Infants are susceptible to pharyngitis, gastroenteritis, and, more rarely, acute hemorrhagic cystitis and hepatitis. More recently, an outbreak in a boarding vocational school indicates that adenoviruses may prevail anywhere there are concentrated crowded conditions and new groups of poten- tially susceptible persons are frequently introduced (222). Adenovirus is also a less common cause of pneumonia in hos- pitalized children as well as gastroenteritis in infants and children, although immunization is not recommended for this population. Adenoviruses have received considerable atten- tion as a defective vector to carry and express foreign genes for therapeutic purposes (223). The genome is easy to manipulate in vitro. Vaccines have been available since 1971 as live, oral, enteric-coated tablets, available in two different strains: type 4 and type 7 adenovirus vaccines. At one time, all military recruits received adenovirus vaccine. Several studies of vac- cine recipients demonstrated a signiﬁcant decrease, generally a 94–100% reduction, in acute respiratory disease due to ade- novirus (224). Unfortunately, production of these vaccines was discontinued in 1996. Between 10–12% of unvaccinated mili- tary recruits become ill with adenovirus infection during basic training. The Department of Defense is currently searching for an alternate source of the product (225).