African countries have the fewest doctors per head of population, with Malawi the worst off.

"Haemagglutinin's a decoy," says Wayne Marasco, an immunologist at Harvard Medical School in Boston. "Those globular heads can undergo many mutations without the virus suffering any ill effects."

He was supposed to be playing in his last World Cup but joined Uwe Seeler, Wladislav Zmuda and Maradona in the record books in the tournament with 21 games before his exit.