In less than a month, unsubstantiated claims about Hillary Clinton's health have gone from chatter on Twitter to an attack line by Republican presidential nominee Donald Trump.

Without offering any evidence, Mr Trump said in Ohio on Monday that she "lacks the mental and physical stamina to take on Isis [Islamic State] and all of the many adversaries we face". Mr Trump, 70, is almost two years older than Mrs Clinton. Most of the latest reports on her health assert that she never recovered from a blood clot that she suffered in 2012, and is keeping her frailty secret.

Her doctors say she fully recovered after surgery. Last year, in a letter accompanied by test results, her personal doctor Lisa Bardack said "she is in excellent physical condition and fit to serve as the president of the United States".

So how did we go from "fit to serve" to "secret health crisis"? Here's how it happened: