Thank you for your inquiry. From what we gather from the question, you were asking about the possibility of HIV Transmission after coming in contact with dried blood and then scratching yourself. From the information given, this scenario is determined to be No Risk (Transmission of HIV is not possible in the given scenario).
The activity you described above is of No Risk because "HIV does not survive long outside the human body (such as on surfaces), and it cannot reproduce outside a human host" (1). Due to exposure to oxygen, HIV undergoes a rapid reduction in concentration. Therefore, in the event that there was dried blood on your fingernails, the virus would be rendered inactive following exposure to oxygen, meaning there is No Risk of transmission from this activity.
Recommendation: There is no evidence or documented cases of transmission.
HIV inactive CDC (1)
AIDS Vancouver Helpline/Online, Ashley
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