BBC reporter on the mood in Mexico City amid empty streets and shops
Governments around the world are hurrying to contain the spread of a new swine flu virus after outbreaks were reported in Mexico, the US and Canada.
At least 100 people are now suspected to have died of the disease in Mexico. The UN has warned the virus has the potential to become a pandemic, but said the world was better prepared than ever to deal with the threat.
Stocks of anti-viral medicines are being readied and travellers are being screened at some airports for symptoms.
Mexican Health Secretary Jose Angel Cordova said suspected swine flu cases in his country had risen to 1,614.
 | SWINE FLU Swine flu is a respiratory disease found in pigs Human cases usually occur in those who have contact with pigs Human-to-human transmission is rare and such cases are closely monitored  |
In the US, where 20 people are confirmed to have caught the virus, a public health emergency has been declared.
There are also confirmed cases in Canada, and investigations are being carried out on possible cases in five other countries.
In most cases outside Mexico, people have been only mildly ill and have made a full recovery.
In other developments:
• Tests are also being carried out on individuals or groups in New Zealand, Australia, Spain, Brazil and Israel who fell ill following travel to Mexico
• World Health Organization (WHO) experts will meet in Geneva on Tuesday to discuss whether to raise the pandemic alert level
• The European Commission also said it was calling an urgent meeting of health ministers to discuss the situation
• The World Bank is providing Mexico with more than $200m in loans to help it deal with the outbreak
• Shares in airlines have fallen sharply on fears about the economic impact of the outbreak
Vigilance urged
The WHO - the UN's health agency - has said the swine flu virus could be capable of mutating into a more dangerous strain.
|  The BBC talks to people in Mexico City about the flu outbreak.  |
In picturesDr Keiji Fukuda, WHO's assistant director-general in charge of health security, said all countries were "looking at this situation very seriously".
"But it's also clear that we are in a period in which the picture is evolving... [and that] we have to be very careful to collect the best possible information," he said.
The WHO is advising all countries to be vigilant for seasonally unusual flu or pneumonia-like symptoms among their populations - particularly among young healthy adults, a characteristic of past pandemics.
Most of those who have died so far in Mexico were young adults.
The H1N1 virus is the same strain that causes seasonal flu outbreaks in humans but the newly detected version contains genetic material from versions of flu which usually affect pigs and birds.
There is currently no vaccine for the new strain, but severe cases can be treated with antiviral medication. Dr Fukuda said years of preparing for bird flu had boosted world stocks of antivirals.
Widespread cases
In the US, eight cases have been confirmed among New York students, seven in California, two in in Texas, two in Kansas and one in Ohio.
| FLU PANDEMICS 1918 : The Spanish flu pandemic remains the most devastating outbreak of modern times - infecting up to 40% of the world's population and killing more than 50m people, with young adults particularly badly affected 1957 : Asian flu killed two million people. Caused by a human form of the virus, H2N2, combining with a mutated strain found in wild ducks. The elderly were particularly vulnerable 1968 : An outbreak first detected in Hong Kong, and caused by a strain known as H3N2, killed up to one million people globally, with those over 65 most likely to die |
The Canadian cases were recorded at opposite ends of the country: two in British Columbia in the west, and four in the Atlantic province of Nova Scotia.
Several other people are being tested for the virus in countries around the world.
A number of countries in Asia and Latin America have begun screening airport passengers for symptoms.
Russia has banned imports of raw pork and pork products from Mexico and parts of the US. But Dr Fukuda said that there was no evidence to link exposure to pork with infection.
In the Mexican capital schools, bars and public buildings remain closed and many people are choosing to stay indoors.
Some people are beginning to worry about the effects swine flu is having on their livelihoods and the Mexican economy in general.
Fear of the virus is expected to lead to many tourists cancelling their holidays and Mexican exports are already beginning to be affected.
 Mexico: 103 dead - 20 confirmed to have died from swine flu, 18 confirmed ill with swine flu United States: 20 confirmed cases of swine flu Canada: 6 confirmed cases UK, France, Spain, Israel, Brazil, Australia and New Zealand: suspected cases being tested |