In an unusual case, researchers have reported how a newborn baby of an HIV-negative mother got the infection from his father who was also suffering from chicken pox.
Fluids leaking from skin blisters of the father was determined to be the source of the infection.
"Transmission occurred during the seroconversion period when the father was unaware of the (HIV) infection and was likely accidental," said the study co-authored by Nuno Taveira of University of Lisbon, Portugal, and colleagues.
Diagnosis of the child happened when he reached age 4.
The results of genetic, phylogenetic, and serologic data analysis on both the father and son and the hypothesis for how the boy became infected were published in the journal AIDS Research and Human Retroviruses.
Based on comparative analysis of the data from the father and the son, the researchers concluded that the virus was accidentally transmitted to the son during the first days of the child's life.
During this time of seroconversion, the father was being treated for infection with varicella-zooster virus (chicken pox) and syphilis when he developed large vesicles all over his body that profusely leaked fluids.
The high virus production early in HIV infection would have made the fluids leaking from the father's skin blisters highly infectious, the study said.
These infectious fluids could have come in contact with the newborn child causing this atypical HIV transmission event.
"This case shows how genetic, phylogenetic, and serological data can contribute for the forensic investigation of HIV transmission," the study added.