Sichuan has confirmed its first-ever case of HIV-2 infection, a rare strain of the virus seldom seen in China, health authorities reported after a detailed laboratory and epidemiological investigation.

The case involved a 67-year-old woman in a county under Meishan city who tested positive for HIV in January. Subsequent confirmatory testing and genetic sequencing verified that the infection was caused by HIV-2 rather than the more common HIV-1 strain, according to a study published in the Chinese Journal of AIDS & STD.

The human immunodeficiency virus (HIV) can be divided into two types: HIV-1 and HIV-2. Due to differences in genetic sequences and structural proteins, HIV-1 has a broader global spread and higher pathogenicity, while HIV-2 is less efficient in transmission and progresses more slowly.