HIV infection probability formula.
Probability of HIV infection = probability of infection of the other party × probability of behavioral infection × probability of missed test.
Instructions for use.
1. Regarding the probability of infection of the other party, if it is determined that the other party is an HIV-infected person or patient, it is calculated according to 100%; if it is not determined whether the other party is infected or not, then it depends on the situation, generally there are such cases.
①, if the other party is a female sex worker, can be considered in accordance with the average 1% calculation (reports vary from place to place, the Internet reports individual places up to 5%)
②, if the other party is a male homosexual, can be considered in accordance with the 5% calculation (there are reports in the UK that believe that the HIV infection rate among the gay population in London is as high as 15%. Some experts estimate that the HIV infection rate among men who have sex with men in large cities in China may be as high as 5%-15%).
③, if it is the general population, calculated according to 0.1% (China’s total population of 1.356 billion, as of the end of April this year, the mainland reported a cumulative total of 203,527 cases of HIV infection, in order to facilitate the calculation, we will temporarily enlarge this data 6.67 times to 1.356 million, resulting in a population infection rate of 0.1%).
④, in the case of intravenous drug users, we can consider an average of 10% (the infection rate of intravenous drug users in London is 4.7%, and 2.3% in the UK; online reports in Xinjiang, Yunnan, Sichuan and other parts of China where the infection rate of drug users exceeds 50%, and the infection rate of local injecting drug users in Yili, Xinjiang is as high as 89%)
⑤. All of the above have geographical characteristics, and in general, exposure to people in high prevalence areas and exposure to people from high prevalence areas should be appropriately adjusted upward in percentage according to local conditions.
2. The probability of being infected through the following various behavioral approaches (i.e., behavioral infection rate. Assuming that the other party has been identified as an infected person).
①.Passive anal intercourse without condom 0.1-3.0%
②, condomless active anal sex 0.06%
③.Passive vaginal sex without condom 0.1-0.2%
④, no condom active vaginal intercourse 0.03-0.09%
⑤, unprotected contact between couples (5 years) 10%
⑥, condom intercourse on the basis of the above probability multiplied by 15%
⑦. Passive oral sex 0-0.04% (In a study of possible modes of transmission among 102 gay and bisexual men newly infected with HIV, the University of California found that eight of the infections may have been due to having unprotected oral sex. (Be careful not to interpret this to mean that the infection rate for oral sex in the population was 8 percent)
⑧, blood transfusion 90-100%
⑨, mother-to-child transmission 20-30%
⑩.needle stick 0.3%
3, complex behavior or multiple behaviors, the probability of infection can be calculated separately and then summed.
4.On the probability of missed test.
①.If HIV antibody test has not been conducted, it is calculated according to 100%.
②. If the antibody test is negative in January after high risk, the missed detection rate can be calculated according to 1% for convenience.
③. If the antibody test is negative in March after high risk, the missed detection rate can be calculated according to 0.1%.
④. If the test is negative after n times, it can be calculated according to the nth power of 1% cumulatively.
This formula is proposed for the first time, we welcome you to follow up with your comments or suggestions as well as updates and more specific information, and will keep the necessary modifications and updates.