Apparently you'd only go to Mexico to eat brain tacos and share needles with cows. Surely there's a better way to filter out risky blood.
It's simple Bayesian probability. Blood tests have a relatively high error rate. Hep-B tests have a 6-12% false negative rate early in the disease, and Hep-C is 3-6% even later in the course of the disease. That's considered a "very low" false-negative rate for a blood test.
In Bayesian terms, blood tests don’t “screen” for a disease. They reduce the odds ratio of contaminated blood by a factor of 10 or so. But the ultimate odds still depends heavily on the prior odds—the prevalence of the disease in the donor population: https://en.wikipedia.org/wiki/Prior_probability. Even with testing, you can reduce the risk of contaminated blood by drawing blood from a pool of donors that has lower prevalence rate of diseases.
Anal sex is inherently much more likely to transit HIV and HIV tests have a higher false negative rate for new infections.
I have never been able to donate blood because of my travels due to their locations and frequencies. I am not going to give up travel to donate blood. MSM is a much higher risk activity than travel, and yet I am also excluded due to my lifestyle risk. It's not fair, but it is reasonable.
12-15% of gay men in the US have HIV.
The rules exist for a very real reason.
But under normal conditions, letting only the best candidates donate is the most efficient way.
if the latter I'm not sure it's enough of a stretch to say unprotected, hi-risk, promiscuity is a risk factor for blood borne illness like HIV? (Such that we need to research it separately)
If you got blood from an addict living on the street engaging in prostitution and tested it, would you trust that blood?
I wouldn't.
https://my.blood.co.uk/eligibility/travel/article?id=47&titl...
Granted it’s shorter, but there are longer wait periods depending on the country. It’s defense in depth because false negatives happen and some viruses take time to show up on tests.
Not quite the four years.
“ If you visited the rural areas of the states - Chiapas, Chihuahua, Durango, Sinaloa districts, Quintana Roo, you need to wait for 4 months after your return to the UK before giving blood. ”
The US rules also aren’t 4 years (not sure why someone told the OP that). It’s 3 years after undergoing malaria treatment. And 3 months after visiting a malaria prone area.
Note: for tattoos, I have no idea if the problem is also related to venereal diseases, or if there is any problem from contamination with the tattoo ink itself, and I don't care enough about this subject to look it up.
Men who have sex with men are something like 50-100x more likely than the general population to acquire HIV. HIV tests do not have a 0% false positive. They will not catch all very recent infections. The rationale for excluding them until recently is that it’s defense in depth and it doesn’t hurt the blood supply much because they only make up about 2-3% of the population.
The current rule is that MSM don’t face a blanket ban, but if you’ve had anal sex in the last 3 months you have to wait because anal sex is inherently more likely to transmit HIV and the tests may not catch a very new infection. Other diseases like Hepatitis have a similar issue.
And yes, you can be very careful and get a disease. But they are playing statistics here: over 60% of injected drug users have Hep-C, that means a lot of prostitutes. They won't and shouldn't trust anyone who say "hey, I had unsafe sex against all advice, but was very careful with the tattoo in a dark cellar and the heroin party, pinky promise".
This is why they usually ask if you've had a new sexual partner in the past 3 or 4 months. This is the window period for detecting some STDs and other diseases.
What's wrong with that? Animal brains are a common dish in many countries, including France, Asia, and parts of the United States
A year later, you go to a blood donation center and they ask you: "Did you go to Mexico in the last N years?"
If you say "Yes", you are banned for four years. If you say "No", you donate liters of blood over the next four years.
If you were in this exact situation, how would you weight which answer is better?