system
Given the following post, respond as if you're commenting on Reddit:
human
How do blood/plasma recipients not get serious viral infections?

If a patient receives whole blood or plasma from a donor, wouldn't viruses like chicken pox, influenza, or even HSV be transmissible via the serum? Even if the original donor has acquired immunity, the recipient's adaptive immune system is not producing T-Cells with the proper antigen receptors. Since many blood/plasma recipients are already immunocompromised, how do they avoid getting horribly sick from latent or active viral infections from the blood they receive?
gpt
They can, and do.  
During the eighties, there were scandals across US and Europe where blood recipients where given blood from HIV+ donors, contracting the disease and dying. This often happened to haemophiliacs as they need donations quite regularly, upping the chances of getting a contaminated one. The scandal was that the companies selling the blood should have tested, but didn't because it was too expensive.   

But other diseases, too, can travel easily via blood donation. This is why blood donors' health is normally closely monitored - or it should be. Who knows in an age where only the quick dollar counts.  
The donated blood, too, gets tested against various antibodies. Unfortunately that's not quite 100% proof either for various reasons - rare pathogens, new variants etc.  
  
There are now two conditions under which you may receive blood: Plannable/selective and emergency.  
  
In the first case, e.g. when the patient is due to undergo an operation where bloods or plasma are likely going to be used, most people will 'donate' their own blood beforehand, thus negating any infection risk save for accidentally being allocated someone else's blood or needing more than planned. This is the much preferred way because it is very safe for the donor/recipient and also cheaper for the hospital as this blood doesn't need to be rigorously tested.  
  
In an emergency, the infection risk takes the backseat over more pressing needs: The patient needs bloods **right now** or else they die. Once the patient is in calmer waters, any infections such as influenza just have to be dealt with.  
  
Haemophiliacs are still at risk.