Moderate HIV viral load the most infectious.In what appears to be a paradox, research has shown that HIV HIV (Human Immunodeficiency Virus), either of two closely related retroviruses that invade T-helper lymphocytes and are responsible for AIDS. There are two types of HIV: HIV-1 and HIV-2. HIV-1 is responsible for the vast majority of AIDS in the United States. may have evolved so that the average viral load viral load n. The concentration of a virus, such as HIV, in the blood. viral load, n a measure of the number of virus particles present in the bloodstream, expressed as copies per milliliter. set-point--around 33 000 copies/ml--seen in most untreated people during chronic infection is finely balanced between being optimal for HIV transmission and optimal for host survival according to according to prep. 1. As stated or indicated by; on the authority of: according to historians. 2. In keeping with: according to instructions. 3. a study published online recently in Proceedings of the National Academy of Sciences The Proceedings of the National Academy of Sciences of the United States of America, usually referred to as PNAS, is the official journal of the United States National Academy of Sciences. . This finding could have implications for HIV prevention, particularly the idea of an 'imperfect vaccine', that is, one that will lower viral load and so allow an infected in·fect tr.v. in·fect·ed, in·fect·ing, in·fects 1. To contaminate with a pathogenic microorganism or agent. 2. To communicate a pathogen or disease to. 3. To invade and produce infection in. person to live longer, rather than totally preventing infection. Given the results of the study the authors warned against other 'imperfect' prevention methods--including immunotherapy Immunotherapy The treatment of cancer by improving the ability of a tumor-bearing individual (the host) to reject the tumor immunologically. There are molecules on the surface of tumor cells, and perhaps in their interior, that are recognized as different from and microbicides. The main aim of this study was to quantify the relationship between viral load and transmission of the virus. Researchers re-examined data from a study on homosexually infected men in Amsterdam and data on viral load and transmission in heterosexual men and women in Zambia. The data from the Amsterdam study suggested that an untreated individual with an average viral load of 1 000 copies/ ml would have 15.6 years of symptom-free life. As the viral load increased, the length of asymptomatic HIV infection asymptomatic HIV infection AIDS A state in which HIV is present in a person without signs of clinical disease; AIDS may follow infection by HIV by up to 10 yrs. See AIDS, HIV. reduced: 9.7 years for 10 000 copies/ml, 4.9 years for 100 000 copies/ml, and 2.1 years for a million copies/ml. Data from Zambia showed annualised transmission rates of 0.02 per year for someone with a set-point viral load of 1 000 copies/ml, to 0.132 per year for 10 000 copies/ml, 0.279 per year for 100 000 copies/ml, and 0.313 per year for one million copies/ml. Researchers found that the periods of highest viral load (during primary infection and during late-stage HIV disease) did not actually have the highest transmission potential: 0.67 (infections per person per lifespan) for primary infection and 0.50 for late-stage HIV disease. In fact, the viral load with the highest transmission potential (of close to 1.5 infections per person per lifespan) was found to be during chronic infection: 33 113 copies/ml. This, the investigators point out, is very close to the average viral load set-point seen in both the Dutch (22 908) and Zambian (54 954) cohorts. Fraser C, et al. Proc Natl Acad Sci 2007. epub October 22. 
What is lifespan in this context? Can the infection rate be extrapolated for very low loads as being virtually one transmission of infection in thousands of years? That was what my extrapolation showed if I understood the data. |
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