Human immunodeficiency virus I and II
Variable. The median incubation period is shorter in infants than in adults.
The time from infection to development of detectable antibodies is generally 1- 3months.
Between 1 and 6 weeks (median 3 weeks) after exposure to HIV, one half to two thirds of recently infected individuals develop a mononucleosis-like illness referred to as the acute retroviral syndrome.
Without treatment, about half of infected adults will develop AIDS within 10 years after infection.
Via sexual route (most common), transfusion of infected blood (or blood products) and contaminated needles; from mother-to-child during in-utero, intrapartum and perinatal period and via breastfeeding. Transmission after contact with saliva, tears, urine, stool and bronchial secretions has not been reported.
Infectious for whole duration of infection; most infectious during the period of seroconversion and untreated late-stage disease when the viral load (measured as number of HIV copies/ml plasma) is very high.
By the end of 2009, there were a total of 4404 cases reported in Singapore (2009 notification rate: 124 per million population). The majority (94%) were infected via the sexual route: heterosexual sex (66%), homosexual (21%) and bisexual (7%). Most cases (90%) are males with the highest proportion (32%) in the 30-39 years age group. There have been 29 children infected through mother-to-child transmission locally.