Nuns wear protective face masks in Mexico City, 1 May 2009

The number of confirmed cases of the H1N1 swine flu virus is rising worldwide -- with nearly all of Mexico, the epicenter of the outbreak, at a standstill in a bid to contain the illness.

Mexico has confirmed 15 deaths from the virus, but the suspected death toll there is more than 160. Mexican authorities report hundreds of additional cases.

Schools, businesses and non-essential offices in Mexico are closed until next week. Many schools have been closed in the United States as well.

U.S. President Barack Obama discussed the outbreak during a meeting with his Cabinet Friday. He said the U.S. is taking the situation seriously and will take every step possible to make sure the American people are safe. He said he is optimistic his government will be able to manage the outbreak effectively.

The U.S. Centers for Disease Control and Prevention report 141 cases of the illness. France, Denmark and Hong Kong confirmed their first cases Friday.

Also, Britain on Friday announced its first case of the illness being transmitted in the country by someone who brought it back from Mexico. Spain and Germany have also documented such cases.

The U.S., with one confirmed death from the virus, has the only confirmed fatality outside of Mexico.

The United States is planning to purchase an additional 13 million courses of flu medicine to add to the national stockpile of treatments for the virus.

Health and Human Services Secretary Kathleen Sebelius said Thursday that 400,000 of those treatments will be sent to Mexico. The U.S. already has more than 70 million courses of antiviral drugs stockpiled across the country.

The U.S. is not closing its border with Mexico, but is advising its citizens to avoid non-essential travel to Mexico. Other countries have made that same recommendation.

The flu has not reached pandemic proportions, but the WHO is asking all countries to combat the spreading virus with "increased urgency."

WHO says the virus also has been confirmed in Austria, Canada, Israel, New Zealand, Netherlands and Switzerland. Suspected cases are being investigated in countries including Australia, Colombia, Japan and South Korea.