The World Health Organization (WHO) chief warned on Monday that swine flu could return with a vengeance. WHO Chief Margaret Chan said that a second wave of the virus “would be the biggest of all outbreaks the world has faced in the 21st century. Twenty-one countries have confirmed cases of the virus which has affected around 900 people worldwide. Chan said the end of the flu season in the northern hemisphere meant that while any initial outbreak could be milder, a second wave could be more lethal, reflecting a pattern seen with the 1918 Spanish flu pandemic that killed up to 50 million people. “We hope the virus fizzles out, because if it doesn't we are heading for a big outbreak,” Chan said, adding that the virus could re-emerge in the coming months “with a vengeance.”
