With confirmation of the first death from swine flu in the United States, public-health officials are struggling to find the way to put preventive measures in place without fueling unnecessary fears.

The Centers for Disease Control and Prevention (CDC) Tuesday morning said a 23-month-old boy in Texas has died of swine flu. The child, who was Mexican, had traveled to the US for treatment. Four students in Delaware are also being tested for the virus. To date, authorities have confirmed 64 swine-flu cases in the United States, in five states.

President Obama said Tuesday he is monitoring the situation. The first confirmed swine-flu death indicates that "this is obviously a serious situation – serious enough to take the utmost precautions," he said. "My thoughts and prayers and deepest condolences go out to the family [of the Texas child], as well as those who are ill and recovering from this flu."

Most reported incidents of flu in the US have been mild so far compared with those in Mexico, where the health secretary said Monday that seven deaths have been confirmed and perhaps 150 more are suspected. Thousands have become ill. [Editor's note: The original text stated a higher number of deaths, which

Mexican officials have revised downward.]

In the US, the outbreak's epicenter is in New York, where health officials have confirmed 45 cases and suspect hundreds more. Two schools have been closed, and officials are considering closing a third.

Mayor Michael Bloomberg says the city is acting out of an abundance of caution, although he does expect to see other cases.

"So far, the swine flu here looks like the garden variety we see every year," says Mayor Bloomberg.

The outbreak in New York was detected last week at St. Francis Preparatory School in Queens, after several students returned from spring break in Cancún, Mexico. Hundreds of students there eventually came down with symptoms, according to Thomas Frieden, New York City health commissioner, but most of the cases were mild and the students are recovering.

Students at two other schools, one public and one parochial, are also being tested for swine flu.

Because most cases involve only mild symptoms, the city has decided not to test every student with a sore throat, cough, and runny nose.

"Our focus now is to very, very carefully look to see if there are any cases of severe illness tied to swine flu," says Dr. Thomas Frieden. "All we're seeing now is a flu season that's a lot later than our usual flu season."

So far, two New Yorkers have been hospitalized: a young boy in the Bronx and a woman from Brooklyn. Both are recovering well, according to Dr. Frieden.

Experts so far applaud the way the federal government and the CDC have reacted, noting the uncertainties that face officials in responding to a new strain of flu.

"We need a sound public-health response, and I worry that people are reading into this rather small problem their horror fantasies about a big problem that hasn't happened yet," says Philip Alcabes, author of "Dread: How Fear and Fantasy Have Fueled Epidemics From the Black Death to the Avian Flu." "We have a public-health system that is capable of controlling these things, and we should take reassurance from a long history of the system being able to do that."