Geneva/Brussels - Health experts appealed for calm Tuesday as the number of confirmed human infections from swine flu in Europe rose to four and governments sent out contradictory signals on how to deal with the spread of the virus. "Nobody should underestimate the situation, but there is no reason to panic either," Androulla Vassiliou, the European Union's health commissioner, said in Brussels.

As of Tuesday afternoon, four cases of swine flu had been confirmed in Europe - two in Britain and two in Spain.

The second Spaniard to be diagnosed with the disease after visiting Mexico was hospitalized in the eastern city of Valencia. Doctors said he was doing well and could soon go home.

Many Europeans travel to Mexico, where most swine-flu deaths have been reported, via Spain. And the Spanish authorities were currently probing about 25 other suspected cases.

Possible infections were also being investigated in the Czech Republic, Austria, Denmark, Germany, Greece, Ireland, Italy, Poland, France and Sweden.

"We expect the situation in the EU to change over the course of the next few days," the EU commissioner said.

Both the EU and the World Health Organization (WHO) have so far ruled out the need to impose travel restrictions to Mexico or other hot spots.

"Border controls don't work, screenings don't work," WHO spokesman Gregory Hartl told reporters in Geneva. "Travel restrictions do not help."

But the French, Spanish and Italian governments were all "strongly" advising their citizens to avoid non-essential trips to Mexico.

The EU has convened an emergency meeting of the bloc's health ministers for Thursday in Luxembourg to forge a common response to the outbreak.

Those talks will focus on how to increase the surveillance of suspect cases, identify such cases quickly, and coordinate precautionary measures, including possible advice to travellers, officials in Brussels said.

The EU executive, the European Commission, also called a meeting Wednesday with pharmaceutical companies to discuss the effectiveness of existing anti-viral drugs and to find out how many months it might take to develop a vaccine.

European governments have in the past refused to create a European stockpile of antiviral drugs for use in the event of an influenza pandemic, and they are still reluctant to release information about their existing stocks.

The WHO also moved to reassure citizens that pork meat is safe.

"There is no danger from eating pork. If you cook pork well, any meat well, it kills any virus," WHO spokesman Hartl said.

EU health experts in Brussels further noted that the EU does not import any pork from the infected areas.

A special helpline in Italy received more than 3,000 calls within six hours of it being opened.

According to reports, most callers wanted to know whether it was safe to eat pork meat, and how they should behave when welcoming relatives back from visits to high-risk areas.

While the virus is most often found in pigs, it has long been known to infect birds, horses and humans as well, say officials at the European Centre for Disease Prevention and Control (ECDC) in Stockholm.

The flu virus now attacking humans is a variant of the H1N1 strain, the most common. Its symptoms are similar to those of seasonal influenza: sudden fever, sneezing, breathing difficulties, and possibly diarrhoea. It also spread in the same way as human flu, via coughing, sneezing or touching an infected surface such as a door-knob.

The ECDC prefers to call the virus "novel influenza" and want to "try to avoid the word swine flu," ECDC Director Zsuzsanna Jakab told reporters in Stockholm.

Its experts noted that April and May are generally mild months and that the continent may benefit from a lull over the summer. (dpa)