People tend to think of viral and bacterial infections as "curable" or at least "preventable" with modern science: given pathogen x, scientists build vaccine or antibiotic, and then you only have to mass-produce it to prevent the spread of disease -- sure, it may take a long time to do the testing and such (regulations slow things down), but it's a solvable problem.
But then there are things like the HIV virus, that we still haven't cured -- and there may not be any cure in the near future, despite the efforts of thousands of scientists and the highest tech on planet earth:
The major obstacle to curing HIV is a vast reservoir of "latent, replication-competent proviruses," which have infiltrated the very cells that help orchestrate the immune response.
Of all barriers to curing HIV, none pose as difficult a conundrum as latency, a quiescent phase in which proviruses essentially lie in wait, but remain capable of reactivation. A provirus is an inactive virus harbored by a cell. And in the case of HIV, the cells that provide a safe provirus haven are the various subpopulations of CD4+ T cells, key members of the immune system.
Obstacle... vast reservoir... difficult... conundrum...
I think, in fact, that it's a lot harder to defend against random viruses and bacteria than people think. So very many tiny objects enter the body each day; and the complexity of screening out the harmful ones is so great, that it's easy to imagine a large percent of new pathogens going undetected by the body's defenses. In fact, I've wondered before whether the body's defenses have the same flaws as certain image-recognition systems -- and even the human brain -- in that they are susceptible to misclassification when fed "adversarial examples"
In this case, it would be malicious particles that have been tweaked ever so slightly so that the immune system doesn't recognize them as such.
If it's so very, very difficult to defend against a random pathogen, just think what that means for the possibilities of bioterrorism. Imagine if Aum Shinrikyo
had come along a little later, in the era of CRISPR and other DNA-modification tools. Just imagine what they might have whipped-up in the lab, and unleashed onto an unsuspecting population -- maybe something like this:
Controversial lab studies that modify bird flu viruses in ways that could make them more risky to humans will soon resume after being on hold for more than 4 years. ScienceInsider has learned that last year, a U.S. government review panel quietly approved experiments proposed by two labs that were previously considered so dangerous that federal officials had imposed an unusual top-down moratorium on such research.