HIV感染の危険因子 CDCのHPから。
CDC, HP: こちら

HIV Risk Behaviors:こちら
医療従事者あるいは性行為を行う人すべてにHIV感染のリスクは存在する。しかし、より安全な医療活動、性行為をすることでそのリスクを最小限にすることができる。

The risk of getting HIV varies widely depending on the type of exposure or behavior (such as sharing needles or having sex without a condom). Some exposures to HIV carry a much higher risk of transmission than other exposures. For some exposures, while transmission is biologically possible, the risk is so low that it is not possible to put a precise number on it. But risks do add up over time. Even relatively small risks can add up over time and lead to a high lifetime risk of getting HIV.  In other words, there may be a relatively small chance of acquiring HIV when engaging in a risk behavior with an infected partner only once; but, if repeated many times, the overall likelihood of becoming infected after repeated exposures is actually much higher. 
The table below lists the risk of transmission per 10,000 exposures for various types of exposures.

Parenteral
Blood Transfusion 9,250
Needle-Sharing During Injection Drug Use 63
Percutaneous (Needle-Stick) 23
Sexual
Receptive Anal Intercourse 138
Insertive Anal Intercourse 11
Receptive Penile-Vaginal Intercourse 8
Insertive Penile-Vaginal Intercourse 4
Receptive Oral Intercourse Low
Insertive Oral Intercourse Low

Others
Biting Negligible(無視可能)
Spitting Negligible
Throwing Body Fluids (Including Semen or Saliva) Negligible
Sharing Sex Toys Negligible


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