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All about HIV Types, Subtypes, Groups and Strains

180px-HIV-SIV-phylogenetic-tree.svgI often get questions from people worried about having some ‘strange strain’ of HIV that cannot be picked up by tests.

Let’s take a step back and try to understand all this rather confusing terms of Types, Subtypes, Groups and Strains of HIV and see if it can shed any light on such concerns.

Scientist love to categorize things into neat little boxes. This is no different for living things. The science of taxonomy is an interesting one. Lets starts with viruses. We all know what viruses are. There are many different Families of viruses. What we are interested in is the Family Retroviridae. In this family, we further sub classify into Sub-Families like Orthoretroviridae. Which we then sub classify into Genus like Lentivirus and again into Species like the Primate Lentivirus Group. Into this neat little box that we have made, lies the HIV virus. i.e. HIV = Family Retroviridae, Sub-Family Orthoretroviridae, Genus Lentivirus, Species Primate Lentivirus Group. The Simian Immunodeficiency Virus also fits into this box but this is just trivia.

There are 2 Types of HIV, Type 1 and 2. They are similar in many ways except for geographical distribution, ease of transmission and speed of disease progression. HIV type 1 is further classified into Groups (M, N, O, P) and subtypes (A, B, C, D, F, G, H, J, K, CRFs). CRF is an acronym that stands for Circulating Recombinant Forms. They are basically products of different HIV subtypes combining together. HIV is classified as such according to their genetic makeup.

So aside from an overwhelming level of complexity that gives scientists a really big kick; what exactly is the use of classifying HIV down to such a degree? The real difference it makes is in people who live with the HIV virus. Knowing exactly the type, group and subtype of HIV we are dealing with makes a big difference in treatment and monitoring.

But what does it mean for people who do not have HIV? Or who have been exposed to HIV and are testing for it? The fact is types, groups and subtypes of HIV are rather geographically distinct. Knowing which predominates in a particular area will help policy makers decide on the appropriate HIV screening tools. Thankfully, most modern tests are able to pick up all forms of HIV. Our clinic uses the Determine and Oraquick rapid tests which are able to test for both HIV Type 1 and 2 and even the dreaded Type 1 O Group.

Although it looks all neat and nice now, the fact remains that science is an ever changing field. No doubt there will be more discoveries of new subtypes and CRFs. We can only hope that testing technology will be able to keep up.

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About Dr. Tan
Dr. Tan graduated from the National University of Singapore in 2001. His residency was in the two largest public hospitals in Singapore; Tan Tock Seng Hospital and Singapore General Hospital.

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31 Comments

  1. hello I am having HIV subtype E which is not prevalent in India. four people injected drug when I was in Thailand and took away my money. I was under depression from last 7 years.

    In India all test comes negative HIV 1 & HIV 2 as well. I came to know that kits available in India cant detect hiv subtype E. I am having CD4 count 500 now and want to start ART treatment. cd4/cd8 ratio is 0.80 less than 1, but dr here are saying you do not have HIV`pls help
    Western blot test for HIV 2shows indeterminate results and showing weak positive results for p26.
    I am having burning sensation in legs and arms. oral thrush like symptoms. sometimes I get burning sensation in thighs and genital area. what other STD can give me such symptoms. Vitamin B12 test done all tests are normal. there is increase in Gamma Globulin 1.33 gm%.in Serum Protein Electrophoresis.

  2. Samir Hussain

    HIV SCREENING : HIV NO BANDS FOR 8 MONTHS,CMIA REACTIVE AS I PREVIOUSLY SAID SIR,ALSO CMIA AB NEGATIVE IN ANOTHER LAB.DEEPLY CONFUSED SIR.AFTER MY FIRST RESULT SHOWED REACTIVE BY CMIA I TOOK INFULENZA(31.07.2013),PCV 13(AUG 16),PPSV23(OCT 16), NOW ON HBsAG VACCINE 20 mcg EACH DELTOID REGION(2ml)21.02.2014 WITHOUT DOCTOR’S ADVICE.NO SPECIFIC EXPOSURE TILL DATE BUT FELL FATIGUE,LIGHT-HEADEDNESS AFTER GETTING VACCINATED TO INFLUENZA,AND THE S/CO VALUE THEN SHOWED
    HIGH. DOES IT MEAN TRANSIENT INCREASE IN VIRAL RNA?BUT WHY ANTIBODIES NOT PRODUCED YET AFTER ALMOST 9 MONTHS? PLEASE REPLY.

    REGARDS
    SAMIR(INDIA)

  3. Samir Hussain

    HIV SCREENING : HIV BY CARD : NO BAND,CMIA :2.57,5.52.6.29,4.94,5.93,5.39,5.29,5.87(<1.00) ELFA : 0.02,0.03,0.04,0.02,0.05,0.04,0.02,0.03(<0.25),W.BLOT FOR HIV1 & 2 NEGATIVE FIRST MONTH.NOT DONE HIV QUALITATIVE PCR.PLEASE SUGGEST.

    REGARDS
    SAMIR (INDIA)

  4. Madison

    Hello Dr. Tan,

    I had a rapid finger prick test and oraquick oral fluid test done a few weeks ago, and my last sexual exposure was 4 years ago. The result was negative. Can the rapid finger prick tests pick up CRFs?

    Thank you for everything

    • CRFs will also induce an antibody response. Modern HIV tests detect the presence of antibodies which indicate a HIV infection regardless of the strain. Please post follow up questions on http://www.askdrtan.com

  5. Hey Dr.tan i just wanted to ask that i recently donated blood to an organization which is registered i guess because they have web page etc. what i wanted to ask was that the aluminium bag from which the guy took out the blood bag was already opened but he did take the cap off from the insertion needle it’s been two weeks i don’t have any symptoms but i am a mode of hyper tension that i might have HIV i called the institution and they said that the blood bags cannot be reused and they cut every needle from after it is used. but some how the tension is not going away. can you please tell me that is it possible for me to have been infected??

  6. Hi please help! I had unprotected receptive anal sex with another male 2 months ago plus, I’ve had tests done at 2 and 6 weeks and the guy I slept with also took at test at 6 weeks, all negative thank god. however still anxious and finding twos situation difficult. I’ve spoken to doctors yet am still curious whether I should look at my 6 week test as conclusive and his test? I had no symptoms (cough,fever etc) but I did have blocked noise and mild sore throat (very mild) I question if it was only in my mind from worrying. anyways I was curious about what you think? thank you it would be a massive relief.

    • It depends on what tests you did. However, most tests would be very indicative at 6 weeks if not conclusive. However, most health authorities still recommend a retest at 3 months. Please post any follow up questions on http://www.askdrtan.com

  7. Dear Dr.Tan ,

    Thanks for the insight . I am an Indian 4 years back I received oral sex from a prostitute in central europe. Since 2 years I am not well .Diarrhea , sweating , skin rashes,running nose ,tiredness and weakness are the few symptoms . I got tested in india with 2 antibody tests ( MEIA, chemiluminescence , 2 rapid , dna pcr , Nat test ,2 westernblots. All negetive. I am still worried as i m not well and think that i m infected by some unusuaal strain or subtype prevelent there which the tests in india are not able to pick.Please suggest ?

    • I do not know of any mysterious subtypes that cannot be picked up by modern HIV tests. If this truly exists and cannot be detected by any tests, then I would not know of it either until some heroic scientist somewhere discovers it.

  8. Hey Dr. Tan I had unprotected sex three years ago and just this past week I took the uni gold test which turned out to be negative but I still have these fears in my head mostly because I have all the symptoms I get cold sores now which I use to never get only when I was a child I’m now 22 and have had 3 this past year , abnomial pains, fatigue…. My main question is does the unigold pick up all strains I live in atlanta ga i know there are alot of strains out there mostly in other countries. I’m just worried because the girl I had unprotected sex with could have been exposed to one of these foreign strains. Also I did have flu like symptoms 2 months after I had sex with this girl ( coughing, chills night sweats) and I never get sick this was actually the last time I’ve been sick.

    • I am not took familiar with the Uni Gold test. Since your concern is the test not being able to pick up all HIV subtypes, I suggest you see a doctor and get a standard ELISA test done. You wouldn’t have the same concerns with the ELISA test. I put much more credence on test results than I do symptoms.

  9. Hi Doctor,

    Nice article. I did an HIV MEIA test 4th generation in the middle east at 12 and 13 weeks after an unprotected fellatio and protected vaginal intercourse. I know it is a low risk. However I would like to know if these tests will detect for sure any group/subtype of HIV and if not would a RNA test be more accurate.

    By was of clarification if there is a new group/subtype would a modern test still detect the HIV virus?

    Thank you very much.

    • I am not aware of any new groups or subtypes that cannot be detected by current tests.

  10. Is there a HIV test, two different people can have done to determine if one person infected the other?

    • Yes. You can take the HIV virus from the 2 individuals and look for unique genetic features. They will not be identical but they can be close enough for us to be reaonsably statistically confident that one of these individuals infected the other.

  11. Dear Dr. Tan,

    I had protected Sex with a working girl about 10 days ago. However, my condom broke and I might have had unprotected sex for abou 3-4 minutes. I could get my penis out before I had an organsm. After I have realized what has happened I was scared as hell and went to the local hospital and started PEP (about 4 hours after) with a local genereica (Zilvarir).
    My questions are: Do have cheap genereica the same effect as original medicines? Does PEP help against Subtype E? The girl has only been working as a prostitute for 3 weeks. I am very scared.

    • I am not aware of any studies on the PEP regime you are on so am unable to comment on its efficacy. PEP works against all subtypes. Please post any follow up questions on http://www.askdrtan.com

  12. Jamie Hazlewood

    Dear Dr Tan

    I would just like to say thank you for your great work and good advice you give here on your website.

    I am in a similar situation to someone who has already posted.

    I recently visited Thailand and had unprotected vaginal sex with a Thai girl I met at a bar. I texted her after with my concerns and she reassured me she wasn’t a typical bar girl and that she regularly got her blood checked so would be clear of any infections. Obviously I don’t know if I can trust this information, I mean why would she get her blood checked regularly anyway?

    Today I had a rapid HIV test (finger prick) and it came back negative. It is exactly 25 days since my possible exposure with HIV. I have been advised to go back in 3 weeks for a conclusive test.

    So I just really wanted to get your opinion and what you think the likelihood is of me having HIV?

    Many thanks

    J H

    • Hi Jamie,

      Totally agree with your conclusions on the girl. Assuming that she was HIV +ve your transmission risk is 1 in 1000 to 1 in 10,000. Acurracy of HIV test at 25 days depends on what type of test was done. Either way, easily more than 90% accurate. I think your chances of NOT having HIV are really good. Please post any folllow up questions on http://www.askdrtan.com

      rgds

      Dr Tan

  13. Dear Doctor Tan,

    I appreciate your efforts and I’d like to ask you a question please. What methods scientists use to discover new types since the HIV antibody/antigen tests seem to be unable to do that? I’m sorry but it seems to be a bit confusing, because you said there’s no doubt that there will be more discoveries of new subtypes and CRFs and we can only hope that testing technology will be able to keep up.

    Thanks in advance.

    • Hi Ginar,

      Current tests are designed to target antigens that are common to all HIV viruses regardless of subtypes, groups or strains. Current research is more aimed at improving sensitivity and specificity and reducing the window period.

      Rgds

      Dr Tan

  14. Dear Dr Tan
    Thank you so much. you have already answer me.π_π
    GOD bless you.

  15. DEAR DR TAN
    I Did’t know how to post to your new forum .
    My mom had blood transfusion on 16 December 2011,She wants plan does HIV antibody test.Last month She also had receiving Gadarsil injection on 21may 2012..my question is Does Gadarsil injection affect the accuracy of test?She will goes
    for test on monday next week 18 june 2012.
    Thank you i am waiting your reply.

  16. Ranjan

    Dear Doctor,

    Came across your website while searching for news on HIV. I would like to your view on my case. i was detected =ve in october 2008. My. VL was 6271 and CD-4 175. I was immediately put on Virady (Atripila). Within 20 days my VL was < 50 but CD_4 never was going up. In fact it had gone down to 134. Thereafter in 2009 I tried some vague medicine (alternative theraphy) and VL was <20 and CD-4 jumped to 396. All along I ws on Viraday. Then in Feb 2011 I stopped the Viraday and tied some herbal tablets. After 45 days my VL was <20 and CD-4 was 515. I felt great and had even put on weight and was generally energetic. After 6 months however my VL was 9300 and CD-4 dropped to 298. So I resumed Virady and VL is <20 and CD-4 has crawled back to about 400. All along since 2008 I have had no symptoms. Is there is any stem cell theraphy which can hold the virus at bay without the daily medication. The daily medication causes depression to no end.

    My age is 51 and weight 74 kg and height 5'-11" and i am from India.

    Thanks for your advise

  17. Martin Chris

    Dear Doctor Tan,

    Your web site is fantastic. Thank you for your great work.

    I hope you can reassure my mind. I read on the net that Thailand has a new subtype E HIV stran that is more contagious and is easier to catch.

    I did something foolish. I was drunk, i massaged with oil and then I gave oral sex to a female Thai bar girl, and I fingered her. I do remember swallowing some of that oil after licking her vegina.

    Post exposure I was tested in Melbourne, Australia post 6 weeks. My test was negative, and the STD clinic here said that this was conclusive, and no other test is required. Since then, I have had major anxiety, have stressed severely. I have had all the usual HIV symptoms, sweats, sore throat, tired, body and muscle aches, glands hurting, fatigue, etc… This has gone on from the beginning (9 weeks now)…. I am worried that the HIV Elisa test did not pick up this Thai subtype E stran, and I might have it.

    The Melbourne STD clinic said that the 6 weeks Elisa test is conclusive, and I did not have to come back, plus they do not know anything about some new subtype stran in Thailand, even though i found this info all over the net….. info says that it is easier to catch, and harder to test for!

    I am worried sick…. The clinic in Melbourne say that they use the best testing in the world…

    Also… 6 week Syphalis, Hap A,B,C, HIV 1,2 all negative.

    What risk did giving oral sex to a lady have, if she was HIV +?
    Also…. Do you know anything about a Thai subtype E stran?

    Should I get tested again…. Please advice… Worried sick!

    • Hi Martin Chris,

      First of all, the chance of you catching HIV from your exposure is next to zero. Secondly, I completely agree with your doctors in Melbourne that the HIV test at 6 weeks is conclusive. Australia is so good at controlling HIV that Singapore sends delegations over to learn from them. So you really should place a whole lot more weight on what your Australian doctors say compared to what I say. A little knowledge is a dangerous thing. It is very easy to spread paranoia by talking about some new super bug that is completely undetectable and goes around killing everyone. There are at least 10 Hollywood movies on that theme. So instead of getting caught up in the latest end-of-the-world-superbug-scare, I suggest you place more faith in your doctors, listen to what they have to say and trust in their professionalism.

      rgds

      Dr Tan

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