MEXICO CITY Fears of a global flu pandemic grew as new suspected cases of a dangerous new strain of swine flu appeared around the world. It has killed up to 81 people in Mexico and spread to the United States and Canada.
Here are some questions and answers about the outbreak:
HOW MANY PEOPLE HAVE DIED? HOW MANY ARE INFECTED?
All the fatalities have been in Mexico, where the government is reporting at least 20 and up to 81 deaths from the flu virus. Most of the dead are between 25 and 45 -- the age group past pandemics have tended to strike.
Mexican officials said, however, that most of the 1,300 suspected cases were found not to have swine flu.
In the United States, the flu has infected 20 people in California, Kansas, Texas, New York and Ohio. Canada has confirmed six cases. Possible infections have also been detected in Spain, France and New Zealand.
WHAT KIND OF FLU IS IT AND HOW IS IT SPREADING?
The virus is an influenza A virus, carrying the designation H1N1 and is spreading from person to person. It contains DNA from avian, swine and human viruses, including elements from European and Asian swine viruses, according to the U.S. Centers for Disease Control and Prevention.
It is passed on by sneezing, coughing or when people pick up the virus from their hands. It likely originated in pigs, but the Mexican government and the World Health Organization have ruled out any risk of infection from eating pork.
HOW SERIOUS IS IT?
The Geneva-based WHO has declared the flu a "public health emergency of international concern." It poses the biggest risk of a large-scale pandemic since avian flu re-emerged in 2003, killing 257 out of 421 infected in 15 countries.
The Mexican government is stressing that it can be treated and it has one million doses of antiviral drugs.
HOW IS THIS FLU DIFFERENT FROM ORDINARY FLU?
The swine flu is characterized by common flu symptoms -- sudden fever, muscle aches, sore throat and dry cough -- but may cause more severe vomiting and diarrhea.
Common seasonal flu kills between 250,000 and 500,000 people in an average year, often targeting the elderly. Most people die from pneumonia and flu can kill previously healthy people for reasons no one quite understands. It can also worsen bacterial infections.
New flu strains can spread fast because no one has natural immunity and a vaccine can take months to develop.
This new strain of swine flu is genetically different from the H1N1 virus that the seasonal flu vaccine protects against.
HOW BAD COULD IT GET?
A 1968 a "Hong Kong" flu pandemic killed about one million people globally. In a 1918 "Spanish" flu pandemic between 40 million and 100 million people died. However, the WHO says the world is now better prepared to withstand a flu pandemic.
WHAT MEASURES IS THE MEXICAN GOVERNMENT TAKING?
Mexico has closed all schools in the capital and two central states until May 6 and stopped hundreds of public events in Mexico City, including concerts.
Mexico City has shut 70 percent of its bars and nightclubs, closed churches and cinemas, and the army is handing out surgical face masks on the street.
The government is recommending people avoid crowded places and refrain from greetings like shaking hands, kissing or hugging. People have been told to wash their hands frequently and avoid sharing food or kitchenware.
It has also issued an emergency decree that gives it the power to isolate sick people, enter homes or workplaces and regulate air, sea and land transportation to try to stop further infection.
The government has even extended the deadline on filing tax returns by a month to the end of May.
WHAT IS THE REST OF THE WORLD DOING TO HELP?
The U.S. government is monitoring developments and the CDC and the WHO are working on a vaccine.
The WHO has activated a command and control center for acute public health events nicknamed the "war room." It says it is ready to use rapid containment measures if needed, including antivirals.
The WHO has a stockpile of 5 million treatment courses of the antiviral Tamiflu, by Swiss drugmaker Roche Holding AG and Gilead Sciences Inc, and of Relenza, made by GlaxoSmithKline, which have both proven effective against the virus.
Countries and regions also have antiviral supplies and the United States has released 25 percent of its 50-million course stockpile of the two drugs.
SHOULD TOURISTS WITH TRIPS PLANNED TO MEXICO BE WORRIED?
The CDC and the WHO say there is no need to alter travel plans and Mexico has said it saw no need to close its borders.
(Writing by Catherine Bremer; Editing by Kieran Murray and Maggie Fox)