From Egypt's order that all 300,000 pigs in the country be slaughtered to travel bans and putting the kibosh on kissing, the world is taking drastic — and some say debatable — measures to combat swine flu.

Egypt ordered the pig slaughter even though there hasn't been a single case of swine flu there. Britain, with only five cases, is trying to buy 32 million masks. And in the United States, President Barack Obama said more of the country's 132,000 schools may have to be shuttered.

At airports from Japan to South Korea to Greece and Turkey, thermal cameras were trained on airline passengers to see if any were feverish. And Lebanon discouraged traditional Arab peck-on-the-cheek greetings, even though no one has come down with the virus there.

All this and more, even though world health experts say many of these measures may not stop the disease from spreading. Today, the World Health Organization raised its pandemic alert to the second-highest level, meaning it believes a global outbreak of the disease is imminent.

"Scientifically speaking, the main thing is that every virus behaves differently," said Joerg Hacker, president of the Robert Koch Institute, Germany's top public health authority. "At the moment, the main issue is to get to know this virus, how it works."

In Germany, where officials confirmed three cases, Lufthansa announced that starting tomorrow it will put a doctor aboard all flights to Mexico, the epicenter of the outbreak.

Experts said that makes sense: The doctors will be able to field questions from uneasy passengers and tend to anyone who might fall ill.

The World Health Organization said total bans on travel to Mexico — such as one imposed by Argentina, which hasn't had any confirmed cases — were questionable because the virus is already fairly widespread.

Roselyne Bachelot, France's health minister, said she would ask the European Union to suspend all flights to Mexico at a meeting tomorrow in Luxembourg.

Travel bans were effective during the 2003 outbreak of SARS in Asia, because that illness can be transmitted only by people who already show symptoms. With flu, by contrast, the incubation period ranges from 24 hours to four days, meaning people often are infectious before they have symptoms.

Health officials don't know enough about swine flu right now to say what the precise incubation period is, but if it's similar to other flu, people are likely able to spread it before they're sick.

"WHO does not recommend closing of borders and does not recommend restrictions of travel," said Dr. Keiji Fukuda, the Geneva-based organization's flu chief. "From an international perspective, closing borders or restricting travel would have very little effect, if any effect at all, at stopping the movement of this virus."

Nor will killing pigs, as Egypt began doing today, infuriating pig farmers who blocked streets and stoned Health Ministry workers' vehicles in protest. While pigs are banned entirely in some Muslim countries because of religious dietary restrictions, they are raised in Egypt for consumption by the country's Christian minority.

Unlike bird flu, where the H5N1 strain that spread to humans was widespread in bird populations and officials worried about people's exposure to infected birds, WHO says there is no similar concern about pigs — and no evidence that people have contracted swine flu by eating pork or handling pigs.

"There is no association that we've found between pigs and the disease in humans," WHO spokesman Dick Thompson said.

Dr. Nikki Shindo, a WHO flu expert, said the agency will consider requests to stop calling the disease swine flu, since the virus is not food-borne and has nothing to do with eating pork.

U.S. Agriculture Secretary Tom Vilsack and others have suggested a new name, arguing that swine flu implies a problem with pork products. China, Russia and Ukraine are among countries that have banned pork imports from Mexico and parts of the United States affected by swine flu.

But some anti-flu measures have merit, such as Obama's admonition today that more American schools might have to be closed temporarily if swine flu cases spread. Already tens of thousands of students in Texas, New York, California, Chicago and elsewhere are out of school.

The WHO said closing schools and public places, along with banning or restricting mass gatherings, can be a way to contain the spread of disease.