Short novel (150 pg about), likely mid-1970s. Going entirely on memory here:
Someone (investigative journalist? conspiracy theorist?) gets the feeling that The Military (US) is doing something very odd in a lab in his town. I recall it being located on the outskirts of a base or airfield, hidden in plain sight kind or thing. He becomes obsessed based on the ridiculous security.
He partners up with someone who is an electronics/computer/security expert and they break in. They end up getting infected with a skin-melting disease. Ends with the disease getting out, and an Air Force general ordering all information about it released to every dermatologist in the world, then killing himself because he has it too.
Don't want to read it again, but it anyone recognizes it:
They find grotesque bodies in the lab, but were they actually aliens like they believed? Or was the whole thing really trying to cover up the disease, not that they had discovered aliens?