World health officials continue to boost their moves to combat the deadly swine flu, releasing millions of antiviral drugs.
The number of confirmed cases in the US doubled to 40 while Britain and Spain recorded their first victims as UN chief Ban Ki-moon warned the new multi-strain virus risked triggering a global pandemic.
"We are concerned that this virus could cause a new influenza pandemic. It could be mild in its effect or potentially be severe," he told reporters, expressing concern that in Mexico most of those who died were young and healthy adults.
Influenza caused three epidemics last century, with the worst being the 1918 Spanish flu, which according to the World Health Organisation killed at least 40 million people.
Mexico, which was rocked by a 5.6 magnitude earthquake yesterday, said the number of confirmed and suspected deaths from the flu had now risen to 149 as other countries urged against non-essential travel to the tourism hotspot.
Europe confirmed its first case in Spain while the Scottish health minister confirmed two cases in Britain. Dozens more suspected cases are being checked in the EU.
Spain is watching 20 suspected cases, Britain 17 and Ireland four, while there were five suspicious cases in Sweden, Denmark and Switzerland, plus four in France and one in Italy. Belgian authorities were examining six people with suspected cases of swine flu, four of whom had returned from Mexico, one from the United States and one from Argentina. Test results from the country's first suspected case were negative.
Nine people each in New Zealand and Colombia, plus one each in Brazil and Peru were under observation with flu symptoms, while in the Middle East, a 26-year-old Israeli was also hospitalised.
Despite 40 cases in five US states, President Barack Obama urged people to stay calm. Only one person was hospitalised and all those infected and who were sick had recovered, US Centres for Disease Control and Prevention acting director Richard Besser said. The ages of patients ranged from seven to 54 years. He said the affected states of New York, Ohio, Kansas, Texas and California and others were receiving 11 million courses of antiviral drugs.
"So the good news is we haven't identified it in additional states. But I wouldn't put too much on that," Dr Besser said, stressing that further nation-wide testing would likely unearth more cases in the next week.
"This virus is acting like a flu virus and flu viruses spread from person to person."
Swiss pharmaceutical group Roche said it was ready to send out more stocks of Tamiflu, some 220 million doses of which are in the hands of governments worldwide.
British pharmaceutical giant GlaxoSmithKline also said it was "urgently" investigating how to boost production of its antiviral drug Relenza as a race to develop a direct vaccine for the H1N1 strain gathered pace.
The European Union called an emergency meeting of health ministers and advised against non-essential travel to areas where the deadly virus has surfaced. The US was also to issue an advisory warning against "non-essential travel" to Mexico.
But Dr Besser rejected the EU warning that appeared to call on Europeans to avoid travel to the United States and Mexico. "Based on the situation in the United States right now, I think it's quite premature to put travel restrictions on people coming to the United States."
The WHO, which upped its alert system from three to four yesterday evening, has warned that the swine flu strain - apparently born out of a mix of human and avian flu viruses that infected pigs - could become a pandemic and called for all nations to "intensify surveillance".
The virus particles can be spread through coughs and sneezes.
The outbreak of swine flu spread fear of economic contagion through financial markets and the travel sector, with losses in European and Asian markets attributed in part to fears of swine flu.