Swine flu has spread to 30 U.S. states and the number of countries with confirmed cases jumped to 19 from two in little more than a week. The expansion comes amid signs of a waning epidemic in Mexico.

Officially called H1N1, the virus is probably circulating in “virtually all” U.S. states, said Anne Schuchat of the U.S. Centers for Disease Control and Prevention. First reported in the U.S. and Mexico, H1N1 also has been confirmed in Central America, Europe, the Middle East, Asia and New Zealand.

The World Health Organization said this weekend it is on the verge of declaring a pandemic, which would mean the new virus is transmissible from person-to-person as it spreads among nations.

Fears that a swine flu outbreak could turn into a global pandemic intensified on Monday, as governments across the globe stepped up their response and tensions rose between Europe and the US following a warning by a senior EU health official against all but non-essential travel to America.

On the first day of trading, financial markets were volatile  after warnings that the flu outbreak in Mexico could become a pandemic and damage any prospect of a fragile economic recovery. Airline, travel, tourism and meat producer stocks fell sharply on swine virus worries, but pharmaceutical stocks rose.

There is no vaccine to prevent the spread of A/H1N1, and even if officials were to start work on one today it would take months to produce.

On the positive side this virus is, at least for now, responding to common antiviral treatments such as Tamiflu. The WHO has an emergency stockpile of 5m or so antiviral drugs, which it plans to make available for the hardest-hit countries.