HIV Infectivity in 24-Year-Old Dried Blood
No, 24-year-old dried HIV-infected blood on a knife is not infectious. HIV is an extremely fragile virus that loses viability within days when dried and exposed to environmental conditions, making transmission from decades-old dried blood essentially impossible.
HIV Survival in Dried Blood: The Evidence
The critical research directly addressing this question demonstrates that HIV survival in dried blood is measured in days, not years or decades:
- Laboratory studies show that when HIV is dried onto surfaces like glass, the virus remains infectious for only several days, with cell-associated virus losing infectivity even more rapidly than cell-free virus 1
- Even under optimal conditions (suspended in serum at room temperature), HIV remains infectious for only several weeks at most 1
- After 24 years of environmental exposure, any HIV present would have been completely inactivated long ago
Why This Exposure Carries No Risk
The virus degrades rapidly when dried due to several factors:
- HIV requires living cells to replicate and cannot survive long-term outside the human body 2
- Environmental factors (temperature fluctuations, oxidation, UV exposure) accelerate viral degradation over time
- The 24-year timeframe exceeds the maximum documented survival period by orders of magnitude
Clinical Context: What Actually Poses Risk
For perspective on actual HIV transmission risks, guidelines define infectious exposures as:
- Fresh blood exposure through percutaneous injury carries approximately 0.3% transmission risk 2
- Mucous membrane exposure to fresh blood carries approximately 0.09% risk 2
- Post-exposure prophylaxis (PEP) must be initiated within 72 hours of exposure to be effective, emphasizing that only recent, fresh exposures pose meaningful risk 2, 3
Important Caveats
This assessment assumes typical environmental storage conditions. The only theoretical exception would be if the blood had been stored under extraordinary laboratory preservation conditions (deep freezing in specialized media), which is not the scenario described here.
No post-exposure prophylaxis or testing is indicated for exposure to decades-old dried blood, as the virus would be completely non-viable 2, 3.