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I thought HIV is a single type of viruses but there are 2 different types. HIV-1 and HIV-2.

SIVsmm virus in sooty mangabeys monkeys and SIVcpz virus in chimpanzees are believed to have crossed the species barrier into humans, resulting in HIV-2 and HIV-1 respectively.

Each virus can be contracted individually, or they can be contracted together in what is referred to as co-infection. HIV-2 seems to have lower mortality rates, less severe symptoms, and slower progression to AIDS than HIV-1 alone or the co-infection. In co-infection, however, this is largely dependent on which virus was contracted first. HIV-1 tends to out-compete HIV-2 for disease progression. Co-infection seems to be a growing problem globally as time progresses, with most cases being identified in West African countries, as well as some cases in the US.


HIV-1 is the most common and pathogenic strain of the virus. Scientists divide HIV-1 into a major group (Group M) and two or more minor groups, namely Group N, O and possibly a group P. Each group is believed to represent an independent transmission of SIV into humans (but subtypes within a group are not).[2] A total of 39 ORFs are found in all six possible reading frames (RFs) of HIV-1 complete genome sequence,[3] but only a few of them are functional.


HIV-2 has not been widely recognized outside of Africa. The first case in the US was in 1987. Many test kits for HIV-1 will also detect HIV-2.

As of 2010, there are 8 known HIV-2 groups (A to H). Of these, only groups A and B are pandemic. Group A is found mainly in West Africa but has also spread globally to  Europe, and the US. Despite the presence of HIV-2 globally, Group B is mainly confined to West Africa. Despite its relative confinement, HIV-2 should be considered in all patients exhibiting symptoms of HIV that not only come from West Africa but also anyone who has had any body fluid transfer with a person from West Africa (i.e. needle sharing, sexual contact, etc.)

Even HIV-1 and HIV-2 have many sub-groups.

Viruses like the West Nile virus (WNV), Zika virus, dengue virus, and yellow fever virus are the same family of virus. Dengue virus also has type-1 and type-2.

4 Answers


I did not know.


Geez, I hadn't really checked it out that much and sure didn't realize that there were two different viruses. Good info Dan.


Dan, I did not know that. Around 1989-1991, I was teaching classes on HIV for Health Care Workers but perhaps the two different strains were not recognized at that time, so long ago?

Also I did not know of the relationship between HIV and West Nile Zika virus, dengue, and yellow fever. 

Rooster Virginia

@Virginia: I can tell you how much the shots hurt with Dengue and Yellow fever. OW!!!!!

TheOtherTink Virginia

@ Rooster:  So do typhoid fever shots.  :O

Dan Virginia

There is no relationship between HIV and the West Nile Zika virus, dengue, and yellow fever virus. I meant that West Nile Zika virus, dengue, and yellow fever virus are related to each other. Also, they all spread by mosquitoes.


No, I didn't know that, and I was even more surprised that HIV is related to the viruses that cause yellow fever, dengue and Zika.

Dan TheOtherTink

No, they aren't. I meant that West Nile, Zika virus, dengue, and yellow fever virus are related to each other. If a person has HIV it won't spread to his cat or dog. Similarly, there is an HIV like virus which infects cats and kills them if not treated but they don't cause anything to Humans and dogs.