European officials are scrambling to protect the continent from a major swine flu outbreak, as first cases were confirmed in Spain and Scotland.

Governments in Europe are still far away from a united response on what the World Health Organization says is a "public health emergency of international concern" that may evolve into a global pandemic.

Some nations have issued travel warnings to the United States and Mexico, with others only urging its citizens to closely monitor the situation in both countries.

European Union Health Commissioner Androulla Vassiliou told reporters that people should "avoid traveling to Mexico or USA unless it's very urgent for them."

The EU said it would summon its 27 health ministers for an emergency meeting to coordinate a response to the spreading swine flu -- but the meeting isn't scheduled until Thursday, and time is running out, observers say.

"If we do not coordinate, individual regions and countries take measures which are inconsistent and create huge economic and personal costs," Robert Madelin, the head of the European Commission's Directorate General for Health and Consumer Protection, told reporters in Brussels.

As of Tuesday, the swine flu had claimed the lives of 152 people, all of them in Mexico, where the disease was first detected.

The flu has since spread to the United States, where some 51 cases have been confirmed, although symptoms outside Mexico seem to be less serious, with no casualties. Authorities can't yet explain why this is; one hypothesis experts have is that the deaths in Mexico are merely the tip of the iceberg, with many more unconfirmed mild cases affecting the larger population. Officials in Israel and New Zealand on Tuesday also reported swine flu cases.

Europeans thought they were safe from the disease until Spanish officials reported that a 23-year-old student who returned from Mexico last week tested positive for the virus. A second case was confirmed by Spain on Tuesday.

Scotland followed, with authorities there reporting two confirmed swine flu cases.

Several countries in Europe have reported suspected cases and are currently testing patients, including France, Sweden, Norway, Ireland and Austria.

Germany on Tuesday became the latest large European country to warn its citizens of a potential flu outbreak as Health Minister Ulla Schmidt announced that three Germans had returned from Mexico with swine flu-like symptoms and were currently undergoing testing for the virus.

Germany had already issued a travel warning to Mexico. German tourism companies have canceled flights to Mexico City, and the Foreign Ministry urged people to carefully monitor the situation in the United States.

A top official from the German Health Ministry, Klaus Theo Schroeder, said Germany is well prepared to handle a potential swine flu outbreak because it has enough medication in stock to treat its citizens.

British Health Secretary Alan Johnson said London has a stockpile of 33 million doses of flu medicine, enough for more than half of Britain's population; France has the same amount, the country's Health Minister Roselyne Bachelot said.

But officials in Europe are eager to prevent a larger outbreak. At several European airports, travelers arriving from affected countries are checked by health officers; governments are stocking up on anti-viral drugs known to work against the swine flu, such as Tamiflu. No vaccine for the swine flu virus exists to date, however. Experts said it takes several weeks to a few months to produce such a vaccine on a large scale.

The last major flu pandemic, an outbreak of the so-called Hong Kong flu in 1968, killed roughly 1 million people around the world. EU officials are optimistic that it won't go that far this time.

"We have to be absolutely vigilant, but we should not create a false alarm," Zsuzsanna Jakab, the director of the European Center for Disease Prevention and Control, an EU science agency based in Stockholm, said Tuesday in a news conference. "During the last three to four years … we have done quite a lot … to make sure that the EU and its member countries are well prepared to meet the challenges to react to even a pandemic."