At least seven people were in U.S. hospitals with swine flu as the number of cases nationwide rose to 68 on Tuesday and a federal health official warned that deaths were likely.
Most of the nation's confirmed cases were in New York City, where the health commissioner said "many hundreds" of schoolchildren were ill with what was "most likely swine flu." The city announced 45 confirmed cases, all affiliated with a Catholic high school.
Dr. Richard Besser, acting director of the federal Centers for Disease Control and Prevention, noted that although ordinary human flu accounts for 36,000 deaths every year, he was concerned by this strain.
"I fully expect we will see deaths from this infection," Besser said at an Atlanta news conference.
New York City Health Commissioner Thomas Frieden said that hundreds of students at St. Francis Preparatory in Queens had developed symptoms consistent with swine flu, although many hadn't been tested to confirm it. Some students there recently went on a spring break trip to Mexico.
"It is here and it is spreading," Frieden said. "We do not know whether it will continue to spread."
In New York, there were growing signs that the virus was moving beyond St. Francis Preparatory school, where sick students started lining up last week at the nurse's office. The outbreak came just days after a group of students returned from spring break in Cancun.
At the 2,700-student school, the largest Roman Catholic high school in the nation, "many hundreds of students were ill with symptoms that are most likely swine flu," said Health Commissioner Thomas Frieden. The cases haven't been confirmed.
Twelve teachers reported flu-like symptoms as well, said the principal, Brother Leonard Conway.
A nearby public school for special education students was shut down after more than 80 students called in sick. Frieden said that some of the students have siblings at St. Francis.
Some of the New York students who tested positive for swine flu after a trip to Mexico passed it on to others who had not traveled — a significant fact because it suggests the strain suspected in dozens of deaths in Mexico can also spread through communities in other countries, said Keiji Fukuda, assistant director-general of the World Health Organization.
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"There is definitely the possibility that this virus can establish that kind of community-wide outbreak capacity in multiple countries, and it's something we're looking for very closely," Fukuda said. So-called "community" transmissions are a key test for gauging whether the spread of the virus has reached pandemic proportions.
The CDC said the country has 68 confirmed cases across six states, with 45 in New York, 13 in California, six in Texas, two in Kansas and one each in Indiana and Ohio, according to the CDC and states. Of the seven hospitalized, two are in New York, three are in California and two are in Texas.
The increase is not surprising. For days, CDC officials have said they expected to see more confirmed cases — and more severe illnesses. Health officials across the country have stepped up efforts to look for cases, especially among people with flu-like illness who had traveled to Mexico.
Plans for a vaccination
Scientists hope to have a key ingredient for a vaccine ready in early May, but it still will take a few months before any shots are available for the first required safety testing. Using samples of the flu taken from people who fell ill in Mexico and the U.S., scientists are engineering a strain that could trigger the immune system without causing illness.
"We're about a third of the way" to that goal, said Dr. Ruben Donis of the CDC.
Test kits are coming to states, so they can perform their own confirmations of swine flu, Besser said. Also, each state has requested its portion of the strategic national stockpile of antiviral drugs, gowns and masks.
“With a new infectious agent, you don’t sit back and wait,” said Besser. “We are in a pre-pandemic period.”
Besser urged people with confirmed cases of swine flu to stay home, and said their family members should stay home, too.
That effectively is a call for voluntary isolation for households in which the virus has been detected. The swine flu appears to be acting like a normal flu virus, which has a fairly high rate of transmission in families, said Besser.
A handful of schools around the country have closed over swine flu fears and some people are wearing masks, but it’s mostly business as usual in the U.S., even at border crossings into Mexico.
While Cuba suspended flights to and from Mexico on Tuesday, becoming the first country to impose a travel ban, and Asian countries deployed thermal sensors at airports to screen passengers from North America for signs of fever, there have been no extra screenings at the U.S. border with Mexico, the country considered ground zero for the outbreak.
No deaths have been reported in the U.S. so far. In contrast, there have been over 150 deaths in neighboring Mexico, with nearly 6,000 people exhibiting symptoms.
'A brand new virus'
Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, testified before a Senate subcommittee Tuesday that this hybrid flu — with pig, bird and human genetic components — has "pandemic potential."
"This is a brand new virus that we've never seen before," he said. "But what we're focusing on is to contain the spread of this."
In the immediate future, cases may begin to level off and dwindle, but then return during the tradition flu season in the fall and winter, as the 1918 flu did, said Dr. Anne Schuchat of the CDC.
"We might see an improvement just like we do with the seasonal flu but we need to be aware this strain is out there and it might come back in the fall," she said. "We're preparing the country for a period of uncertainty and a commitment that we'll stay with you."
Scattered protective steps were being taken across the U.S. A few schools were closed — in Cibolo and New Braunfels, Texas; Claremont and Mira Mesa, Calif.; and Columbia, S.C. — and residents of Guadalupe County, outside San Antonio, were asked to avoid public gatherings and stay home if they are ill.
Security guards at all entrances of the University of Chicago Medical Center required anyone walking in to use a liquid disinfectant. At Rush University Medical Center, anyone seeking treatment for fever, runny nose and coughs was being tested for flu with nasal swabs.
Elsewhere, there were signs of growing unease among the public, even in places where there was no immediately known cause for alarm.
Pharmacies in Manhattan reported that paper face masks were selling by the box. One pharmacy owner said he had to order more from his wholesale supplier for the first time since the SARS epidemic six years ago.
Students at a Chicago school were instructed not to shake hands with anyone, and Southern Illinois University urged students to wash their hands frequently and cover their mouths when coughing. There were no known swine flu cases in Illinois.
And in New Mexico, which also had no reported cases, health officials were so besieged by calls from concerned citizens that they set up a swine flu hot line.
Besser, of the CDC, said his agency was looking for evidence of the disease spreading and probing for ways to control and prevent it.
The government also issued an advisory warning for travelers to cancel any nonessential visits to Mexico. It also took issue with a European Union health official who said the same thing about travel to parts of the U.S.
At the White House, a swine flu update, delivered by White House homeland security adviser John Brennan, was added to the president's daily intelligence briefing.
FDA issues emergency flu drug rules
The Food and Drug Administration issued emergency guidance late Monday that allows certain antiviral drugs to be used in a broader range of the population in case mass dosing is needed to deal with a widespread swine flu outbreak.
The agency originally approved the use of the antiviral drug Tamiflu for the prevention and treatment of influenza in adults and children age 1 and older. Another antiviral drug, Relenza, was originally approved to treat people 7 and older and to help prevent flu in those 5 and older.
The White House also aimed to sidestep a potentially problematic diplomatic headache. Press Secretary Robert Gibbs declined to discuss whether Obama officials have any concern about when Mexico notified the U.S. of the outbreak — particularly significant given the president's trip to Mexico on April 16 and 17.
The White House said Monday that its medical unit asked if Mexican health officials and U.S. Embassy medical staff had any concerns about infectious disease and were told they did not. But a White House statement said, "We have no reason to believe they withheld any information they had at the time."
The Associated Press contributed to this report.