摘要
1型（HIV-1）和2型（HIV-2）HIV属于慢病毒属逆转录病毒科。不同种病毒传播到人类很可能是通过打猎或处理“丛林肉”过程中血液污染造成的。相关病毒感染猫、马、山羊和绵羊，引起慢性感染，有时造成免疫缺陷。HIV-1源自黑猩猩的恒河猴免疫缺陷病毒（SIVcpz），而HIV-2在遗传基因上与乌黑白眉猴病毒相近（SIVsmm）。因此1型和2型HIV存在着差别，它们的核酸序列只有40％的同源性。在自然界，SIV并不引起灵长类宿主的免疫缺陷，但1型和2型HIV对人类都有致病性。
HIV-1 and HIV-2 are members of the lentivirus family of retro-viruses. Cross-species transmission into humans most likely occurred by blood contamination through the hunting and handling of ＇bushmeat＇. Related viruses infect cats,horses, goats and sheep, causing chronic infection and, in some cases, immunodeficiency. HIV-1 is derived from the simian immunodeficiency virus of chimpanzees（SIVcpz）, whereas HIV-2 is genetically closer to the sooty mangabey virus （SIVsmm）. As a result, HIV-1 and HIV-2 are relatively dissimilar;, their nucleic acid sequences are only about 40% homologous. Neither SIV causes immunodeficiency in its native primate host, but both HIV-1 and HIV-2 are pathogenic in humans.
