Strawman Has a Point: Leavitt is revealed to be epileptic in the final act; Hall sympathizes with the secrecy because in The '60s, epilepsy was considered little different from Down's Syndrome - a deal-breaker that would keep a truly brilliant man from working in any lab more important than a high school(and the source of his anti-establishment mindset). But even forgiving that, it really is a disability, as his condition made him black out during testing and miss a vital clue as to destroying the Strain.
Too Dumb to Live: Leavitt enters the Wildfire facility fully admitting to a phobia of red lights - actually covering for her photosensitive epilepsy that will paralyse her and turn her into a convulsing lump. The facility science experiments have flashing red lights when a success is recorded. Leavitt nearly destroys the world when she goes catatonic when a red flashing light signifies a cure has been discovered on her watch.
In fairness to the character, however, she didn't know going in that the lab used that kind of alert signal, didn't realise she had blacked out when it first displayed (as she, like all the characters, was already running on the ragged edge of exhaustion at that point), and is pragmatic enough in the face of the failsafe device that one may freely theorise that she would have confessed her problem if she had had time enough to realise how it might affect their work.
Anvilicious: Robert Shenkkan, true to form, claimed it was his "obligation" to change the novel's story and make the main scientists race-mixed with a homosexual member who keeps his head cool when others don't.