Back in about 2000, we had a passenger onboard from somewhere in South America. He boarded in Miami and was going to New York. It was a red eye flight, which I try to avoid, but I was the only pilot (Capt.) that was available in Miami to bring the B-757 north to NYC.
This man was hacking and coughing even before he boarded. Generally, passengers will sleep on red eye flights, but that wasn't going to happen with this guy onboard. The person seated next to him complained to the F/A about his coughing, so she reseated him to the rear of the plane. That didn't help and more passengers were complaining. This guy coughed the whole way to NYC and I don't mean just a little cough, but a real deep down cough.
When we arrived in NYC, I suggested that he be checked before going out into the public, but the gate agent said he was already checked in Miami when he went through immigration and customs. I told her that I thought this guy slipped through the cracks, so she had him isolated and an EMT we had on staff in Miami checked him over and said that she thought he should be sent to the hospital for further evaluation.
Later in the afternoon when I went back to the airport to catch my flight to Chicago, I was told that this man was diagnosed with some form of Meningitis. The airline ended up calling everyone that was on the flight and warned them of this situation and told them that they suggested to visit a doctor and send them the receipts for reimbursement.
My doctor sent me to the nearest hospital in NYC and I received an IV of Gamma Globulin and a prescription for some antibiotics, which I forget the name. You just never know what to expect.