To investigate an intra-familial transmission event of human immunodeficiency virus type 1 (HIV-1) using molecular epidemiological method, and to elucidate the spreading route among the family members.

Epidemiological investigation, including follow-up and testing, was conducted for a pregnant woman who was anti-HIV screening-reactive, her husband and their newborn. Viral RNA was extracted to amplify HIV-1 gag gene and pol gene segments with one-step RT-PCR. Phylogenetic tree was constructed to analyze the spreading route.

The proband (EID1107M) was a pregnant woman who was found to be HIV-seropositive during pregnant care. Her husband (EID1107F) was then confirmed to be anti-HIV positive. Her newborn (EID1107I) was positive for HIV-1 nucleic acid at age of eight months. All three patients were infected with HIV-1 CRF02_AG strain. Phylogenetic tree showed that the three patients formed a subcluster with high genetic homogeneity. The topological structure indicated the transmission route was from the father to the mother, then to their child.

Contagious diseases screening should be reinforced before marriage and during pregnant care. Prevention of mother-to-child transmission should be timely and efficiently administered upon diagnosis of infection, to avoid the secondary intra-familial transmission and to improve the population quality at birth.

Human immunodeficiency virus type 1; Intra-familial; Mother-to-child transmission; Molecular epidemiology