The Obama administration may have had a brush with the swine flu outbreak after a member of the White House advance team on Obama's recent trip to Mexico apparently came down with the disease.
White House press secretary Robert Gibbs said the staff member, whom he did not identify, began to feel ill April 16 after he accompanied Secretary of Energy Steven Chu to Mexico in advance of Obama's arrival. Two days later, Gibbs said the staff member returned to the United States on a United Airlines flight to Dulles International Airport outside Washington, D.C.
On April 28, the individual's wife, son and nephew tested positive for H1N1, Gibbs said, adding that samples had been sent to the U.S. Centers for Disease Control and Prevention in Atlanta to determine if it is the same strain of H1N1 that now threatens to spark a global pandemic.
Though President Obama was in Mexico at the same time as this individual, Gibbs said the staff member never came within six feet of the president. Neither Obama nor Chu has shown any symptoms and neither has been tested for the flu.
Gibbs said the staff member likely carried the virus on the flight home from Mexico.
"The family members experienced mild to moderate symptoms, received no medications and recovered," Gibbs said, adding that the individual is back at work today.
The administration staffer tested negative, which Gibbs noted was "likely because so much time had elapsed since the onset of his own symptoms that they would not show up in the test."
Gibbs said he is not aware whether health officials will try to contact people who were on the flight from Mexico with the staff member.
The revelation came on a day that the CDC case count rose to 109 confirmed infections in 11 states. South Carolina was the newest addition to the official list of states affected.
State health officials, however, have reported a number of cases that have not yet been confirmed by the CDC. Adding these results -- including the first two cases in Virginia announced Thursday evening -- would mean a total of at least 134 cases in 19 states.
On Thursday, the swine flu outbreak caused schools in 14 states to shut their doors on more than 160,000 schoolchildren, and additional closures could affect as many as 223,700 students in 17 states.
In total, more than 100 school systems have closed at least one school as the nation tries to stifle the spread of the disease. In Texas Wednesday night, officials announced that the entire Fort Worth school system would be closed through at least May 8 as a precaution, idling 80,000 children in 140 schools.
"We're asking for flexibility, and I'm sure our business community can come up with creative ideas, rotating shifts, without creating hardships on families financially," said Melody Johnson, Fort Worth schools superintendent.
While most Fort Worth parents seem to support the district's decision, experts question if it's necessary to shut down an entire district for a single case of the swine flu.
"It's too soon to tell what's the best approach, but we will be looking at what people are doing, and learning from it as it goes forward," said Julie Gerberding, former head of the CDC.
Richard Besser, acting director of the CDC, said that health officials hoped the closures would help stem the spread of the virus in affected states, although he added that it remained to be seen whether the strategy would actually work.
"We want to make sure that school closure is in fact lowering the risk of spread in a community," Besser told "Good Morning America" Thursday. "The goal is not to send the children out into the community."
Vice President Joe Biden said on "GMA" Thursday that he hoped that parents would be able to make adjustments as their children's schools -- and possibly their own workplaces -- shut down to limit the threat of swine flu spread.
"Our hope is that employers will be generous in how they treat that employee," Biden said.
The school closures cap off several frenzied days of adjustments by federal and state governments to stem the spread of the virus.
New York State Hardest Hit
And the spread appears far from over. A 30-year-old female from Kentucky with a confirmed case of swine flu is currently hospitalized in serious condition at West Georgia Medical Center in LaGrange. The woman had recently traveled to Cancun and was in Georgia for a wedding when she became ill. She has been in the hospital since April 26.
In Washington, D.C., the World Bank issued a statement Thursday morning that a staff member who had traveled to Mexico on business April 14-18 had been "preliminarily diagnosed" with swine flu. The CDC has yet to confirm the diagnosis of that individual, who is a Maryland resident, according to the statement.
The World Health Organization raised its pandemic flu alert again Wednesday to phase 5, which denotes that a pandemic is imminent. On Thursday, WHO reported that the number of lab-confirmed cases worldwide rose to 236, up from 148 on Wednesday.
In Mexico, where the flu outbreak was believed to have started, the government took more drastic action Thursday, ordering all nonessential businesses to close.
Mexican President Felipe Calderon, who has been criticized for his low profile during the crisis, addressed the nation Wednesday night and told Mexicans to stay home.
"There is no safer place to protect yourself against catching swine flu than in your house," he said.
On Thursday, Switzerland, the Netherlands and Peru became the latest countries to report swine flu cases, which have now been reported in at least 14 countries.
The first death from swine flu in the United States occurred Wednesday, when a 22-month-old baby boy in Texas died.
The worst hit state so far is New York, with 51 confirmed cases.
Mayor Michael Bloomberg originally said Monday that the cases were confined to a "single cluster," to students at St. Francis Preparatory School and their relatives. Several of the students had spent spring break in Cancun, Mexico.
Since then, Bloomberg has confirmed that it had spread to several other schools and that hundreds of children could be suffering from the virus. New York City Health Commissioner Thomas Frieden said that "many hundreds" of students and teachers at St. Francis are sick, although most of those cases appeared mild so far.
"It is here, and it is spreading," Frieden said. "We do not know whether it will continue to spread."
"I do expect more cases and expect more states to be affected," Dr. Anne Schuchat, interim deputy director for the CDC's science and public health program, told a Senate hearing Wednesday. "I think we need to be prepared that even if it starts to look a little better, it may get a little worse."
To fight the epidemic, the Obama administration is asking Congress for $1.5 billion. White House press secretary Gibbs said the president was requesting the funds "out of an abundance of caution" to "enhance our nation's capability to respond to the potential spread of this outbreak."
The CDC has become the center for the swine flu investigation. It is one of only four laboratories in the world that have the expertise to unravel a novel flu strain.
"What we're trying to do is to identify how bad, how good, the swine flu is currently operating -- is it expanding, is it contracting, is it maintaining a steady state," said Phillip Navin, director of the Division of Emergency Operations at the CDC.
With the uptick in cases, the CDC shipped more antivirals and sent additional teams into the field.
"I think at the moment we need to be looking forward and making sure that we're doing everything that we can to keep people from getting sick," said Dr. Steve Reed, director of the CDC's Influenza Coordination Unit.
Swine Flu Ground Zero
Mexico, the country worst hit by swine flu, has taken dramatic action over the last few days in attempting to contain the virus. While authorities hunt for the source of the swine flu outbreak, the country is under lockdown. It has taken the drastic step of ordering a suspension of all nonessential federal government and private business activity.
In a televised address, President Calderon praised "the heroic work" of doctors and nurses and asked his countrymen to literally stay in their homes between May 1 and May 5, saying, "there is no safer place to protect yourself against catching swine flu han in your house."
"In recent days, Mexico has faced one of the most serious problems in recent years," Calderon said Wednesday night. He brushed aside criticisms that his government's response had been slow, emphasizing several times that authorities had reacted "immediately."
But with the flu spreading quickly in the United States and across the globe, the actions of Mexican health officials are under the microscope. Many health experts question whether the government has done enough to contain the flu.
Oscar Barrera, who was diagnosed with the flu Monday and prescribed Tamiflu, said he was sent home by medical officials and simply told to keep away from other people.
Barrera claimed that health officials did not test his pregnant wife and three-year-old son, or anyone in the cell phone shop where he worked, for the flu.
"What worries me most is if the officials don't do enough to protect my family," Barrera told ABC News.
According to Mexico's health ministry, there now have been 12 confirmed deaths of the swine flu in Mexico, but roughly 176 deaths are suspected of having been caused by the virus. There are nearly 3,000 suspected cases.
Schools, museums, parks and churches in Mexico City have been shut down by the government. A leading business group estimated that canceled events and closure of establishments to prevent the spread of swine flu is costing Mexico City at least $57 million a day.
All of Mexico's Mayan ruins and Aztec pyramids have also been shut down until further notice.
Mexican officials are hoping the 10-day shutdown will be enough to cover the two-day incubation period and the seven-day recovery of anyone who has the virus.
Mexico's first suspected case of the swine flu was detected in the remote farming village of La Gloria, where 5-year-old Edgar Hernandez contracted the disease nearly one month ago, authorities said.
"The most likely way that this young boy got the infection was from another person who had been in contact with the pigs," said Dr. Kathryn Edwards at Vanderbilt Medical Center.
More than 800 people in the town of 2,000 were infected, authorities said, but no deaths were reported. It took seven days for Mexico to confirm its first cases of swine flu, according to World Health Organization estimates.
Officials said it's still too early to determine how the disease spread from La Gloria into a global health emergency.
The Associated Press contributed to the reporting of this story.