recovery of illness, adenoviruses may maintain latent persistent infections in the tonsils, the adenoids, and other lymphoid tissues of man, and they are readily activated. (Most persons are infected with one or more types of adenovirus before the age of 15, 50 to 80% of tonsils removed surgically yield an adenovirus when cultured in vitro). Ad1, Ad2 and Ad5, members of subgenus C, persist in tonsils for several years. Shedding of infectious virus in the stools for at least 2 years have been documented. Adenovirus strains can also be secreted in the urine.

Clinical syndromes
1. Pharyngitis
2. Pharyngoconjunctival fever
3. Acute respiratory disease of recruits
4. Pneumonia
5. Follicular conjunctivitis
6. Epidemic keratoconjunctivitis
7. Petussis-like syndrome
8. Acute haemorrhaghic cystitis
9. Acute infantile gastroenteritis
10. Intussusception
11. severe disease in AIDS and other immunocompromized patients
12. Meningitis

Respiratory Disease in Children
Adenoviruses are responsible for 5% of acute respiratory infections in children under the age of 4 years, whereas they account for 10% of hospitalized respiratory infections in this age group. Adenoviruses can also cause laryngotracheobronchitis, but the pneumonias which occur in young children are the most serious manifestations. These may occur as a consequence of infection with the endemic Ad2 and Ad5, among which certain strains can be more aggressive than others. In particular, Ad 3 and Ad7, may also create severe problems. Adenoviruses have been reported to account for 10% of pneumonias of childhood. The severity of symptoms is related to vercrowding. In the winter of 1959, 3398 cases of adenovirus pneumonia with a fatality rate of 15.5% were seen at the Peking children's hospital. Among the survivors of severe respiratory infections, residual lung damage due to secondary obliterative bronchiolitis has been reported. Bronchiectasis and abnormal lung function tests have also been reported as sequelae.

Sources of exposure
The main source of exposure is thought to be contact with infected individuals,with transmission of viruses by inhalation of aerosols. Contaminated water is another possible source, with infection occurring by ingestion, inhalation of aerosols, or direct contact with the eyes. Several large out- breaks of pharyngoconjunctival fever caused by adenovirus serotypes 3 and 4 have been asso- ciated with swimming pools. As viruses only replicate in living host cells no increase in numbers will occur in the environment.

Pharyngoconjunctival Fever
This disease is characterized by conjunctivitis, fever, pharyngitis and adenoidal enlargements. This is frequently associated with swimming pools. Adequate levels of chlorine are usually sufficient to in- hibit outbreaks.

Acute Respiratory Disease (ARD) in Military Recruits
ARD is usually caused by Ad4, Ad7, and Ad21, although Ad14 has been reported from Holland. In general, outbreaks do not involve seasoned troops but cause a high morbidity among newly
enlisted troops. Adenovirus infections among healthy civilian adults are less common. The crowding of people, allowing repeated exposure to highly infectious doses, and the strenuous physical ex- ercise may account for the unusually high degree of severe infections. ARD usually appears during the third week in training. Characteristic symptoms include fever, malaise, sore throat, hoarseness and cough. Pneumonia develops in around 10% of cases. Pertussis - Adenoviruses can be isolated frequently (39%) of patients infected with B. Pertussis. The contribution, if any, of adenoviruses to the pertussis syndrome is not known.

Infections of the Eye
Acute follicular conjunctivitis, which is part of the syndrome of pharyngoconjunctival fever, can also occur as a separate entity. The disease is also associated with swimming pools. Epidemic kerato- conjunctivitis is a distinctly different syndrome. This syndrome is characterized by an aggressive conjunctivitis, pain, photophobia and lymphadenopathy followed by the development of superficial punctate keratitis, corneal opacities may last for several years. In 1941, more than 10,000 cases occurred in the marine shipyards of Pearl Harbour ("Shipyard eye"). Adenovirus keratoconjunc- tivitis mainly affects males in Western countries or children in Asia and may last for 4 to 6 weeks. Antibody to Ad 8 is uncommon in American school children, whereas approximately half of the Japanese or Taiwanese children have such antibodies.

Acute Haemorrhagic Cystitis
This syndrome occurs predominantly in 6 to 15 year old boys. The syndrome consists of acute dysuria with haematuria and is mainly associated with Ad 11. Its significance lies in the potential of being confused with more serious diseases of the kidney such as glomerulonephritis.

Infections of the gut
Adenoviruses are associated with 4-15% of all children hospitalized with viral gastroenteritis.
Gastroenteritis may be a sign of a systemic infection such as those caused by Ad3 or Ad7. They may cause both respiratory and diarrhoea in a child with high fever. However, the enteric adenoviruses Ad40 and Ad41 are associated with 2/3rds of cases of adenovirus-associated diarrhoea. Several reports have appeared implicating adenoviruses in mesenteric adenitis and intussusception of the gut.

Meningitis
Adenoviruses may be infrequent cause of meningitis. Ad3 and Ad7 account for two-thirds of all adenovirus-associated meningitis.

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