On Monday, in reponse to a growing swine flu epidemic, the World Health Organization raised the pandemic alert level from three to four, meaning there is sustained human-to-human transmission of the virus. Level six represents a full blown pandemic.
The number of people thought to have died from the disease reached 152 — all of them in Mexico, where the outbreak began.
Beyond Mexico, the United States and five other countries were dealing with confirmed cases of the flu. The United States is now reporting at least 68 confirmed cases; Canada is reporting six, and a few cases are confirmed in the United Kingdom, Spain, Israel and New Zealand. Suspected cases have been reported all the way from South America to Asia.
Many more countries were taking steps they hope will keep it away, tightening borders and immigration controls as the swine flu epidemic spread. Cuba suspended flights to Mexico, and countries including the United States, Canada and France warned their citizens to avoid nonessential travel to Mexico. Russia, Hong Kong and Taiwan all said they would quarantine any ailing visitors who come from countries where the disease has been discovered.
Martin Blaser, a former president of the Infectious Diseases Society of America and the current chairman of the Department of Medicine at the New York University School of Medicine, joins Martin Savidge to discuss how governments are responding to the outbreak and how widespread this strain of flu is.
View a map detailing the spread of the swine flu: