Apparently that’s what a flight crew on a Korean Air flight to Auckland thought when they alerted police on the ground that a passenger was vomiting, or "displaying bird flu symptoms".  According to an AP report in the New York Times today:

Crew on the flight, from South Korea via Australia, alerted airport authorities when the woman began vomiting and showing other possible bird flu symptoms, sparking a lockdown on the tarmac as the plane landed, said Norman Upjohn, an ambulance duty manager.
The 223 people aboard the Boeing 747 were held for about an hour under ”full quarantine procedure” while a paramedic in protective clothing examined the woman, Upjohn said.

South Korea declared itself bird flu free in June, after reporting no new cases of the H5N1 strain of bird flu — in birds or humans — for three months.

I sure hope that no one with a bit of vomit or diarrhea flies to NZ from the UK this week.