Design: Randomized clinical trial involving hospitalized HIV-1 infected children. Children will be randomized to randomized to urgent (<48 hours) versus early antiretroviral therapy (7-14 days). This trial will be unblinded.

Population: Hospitalized HIV-1 infected children who are antiretroviral therapy (ART) naïve ≤ 12 years of age.

Sample size: 360 children will be randomized (180 per arm).

Treatment: All infants will be treated with ART according to World Health Organization (WHO) and Kenyan national guidelines.

Study duration: Enrollment into the study will occur over the course of 36-48 months and each infant will be routinely followed for a maximum of 6 months.

Study site: Kenyan hospitals.

Primary hypothesis:

HIV-1 infected children hospitalized with severe co-infection either may be unsalvageable due to too far advanced immunosuppression/co-infection or may benefit from urgent ART.

Secondary hypotheses:

Urgent ART during an acute infection could potentially result in increased risk of immune reconstitution inflammatory syndrome (IRIS) or drug toxicities/interactions.

Specific aims:

1. To compare the 6 month all-cause mortality rate, incidence of immune reconstitution inflammatory syndrome (IRIS), and incidence of drug toxicity in HIV-1 infected children (≤ 12 years old) presenting to hospital with a serious infection randomized to urgent (<48 hours) versus early ART (7-14 days).
2. To determine co-factors for mortality, IRIS, and drug toxicity. Potential cofactors will include: baseline weight-for-age, height-for-age, weight-for-height (Z-scores), CD4, HIV-1 RNA, type of co-infection, age, rate of viral load and CD4 change following ART, immune activation markers, pathogen and HIV-1 specific immune responses.

Secondary aim: To determine etiologies of IRIS and to compare immune reconstitution to HIV, TB, EBV and CMV following ART overall and in each trial arm.

Children will be followed and compared for 6-month mortality.

Inclusion Criteria:

• Aged ≤ 12 years old (reported)
• HIV-1 positive (for example, two rapid HIV-1 antibody tests for children >18 months and not breastfeeding, or one HIV-1 DNA/RNA test for children ≤18 months or who are breastfeeding)
• Not currently receiving antiretroviral therapy (history of pMTCT does not affect eligibility)
• Eligible to receive ART, according to current WHO guidelines
• Caregiver plans to reside in study catchment area for at least 6 months (reported)
• Caregiver provides sufficient locator information

Exclusion Criteria:

• Suspected meningitis, any other central nervous system infection, or encephalitis

after primary and secondary outcomes are published

6 months