It's another example of survival bias .... we only automatically count the survivors of any given situation but never think of the individuals that died in the process.

Klingons survived through that period of their history because so many others had to die needless, pointless, helpless deaths because of infections, diseases and suffering while a few went on to become stronger more resilient individuals.

It's the same in human history ... we got to the modern age with a much stronger immune system because so many millions had to die hundreds of years ago before we developed immunity.

If we allow Discovery as evidence, Klingon technology has been in steep decline for centuries, only recently falling to as primitive as 24th century Federation technology.

It's possible that Kligons had better medical treatments available in the 21st century than in the 24th.

Idk they have pretty robust immune systems

I mean it cured the phage

This may explain Klingon blood being red sometimes and pink sometimes. Maybe one or the other is just a symptom of space syphilis.

Kahless got the clap…

"Our STIs are dead. Ancient Klingon warriors slew them a millennia ago. They were more trouble than they were worth."

With Glory, it’s just a hole

You forget that anatomically Klingons are very redundant and are excellent healers and have extremely strong immune function. Like in Voyager, those organ harvesting people wanted the half-Klingon because she's(Torres) immune to the plague (phage) decimating their people.

"Blood-borne diseases" would make more sense, given that you're talking about blood and not sex.

Klingons have very different anatomies and immune systems to humans, it's a good chance blood borne diseases don't even affect them all that much.

It was never a problem for your mom.