"While reports from Mexico are -- appear to be encouraging, and some are cautiously optimistic, we can't afford to let down our vigilance," the Centers for Disease Controls's Rear Admiral Anne Schuchat said today. "We have information that this novel virus continues to spread, with increasing cases and increased states affected."
School closures, asking individuals who feel sick to stay at home and hand washing are all preventive elements, officials have said.
In the United States, there are 160 confirmed cases in 21 states, Schuchat said. One person has died from the flu in this country, a toddler who died last month in Texas. In Mexico, 16 people have died.
"The majority of cases don't have direct contact with Mexico. They didn't travel to Mexico," Schuchat said. "It is much more likely that people are getting this particular infection now from somebody ... within their own communities. You know, we do think that there's sustained transmission here in the U.S. in several areas."
According to the World Health Organization, a total of 16 countries now have at least one case of the disease, also known as H1N1 flu, and the overall number of confirmed cases has risen to more than 650.
"This is a new strain of the flu virus, and because we haven't developed an immunity to it, it has more potential to cause us harm," President Obama said in his weekly address today. "Unlike the various strains of animal flu that have emerged in the past, it's a flu that is spreading from human to human. This creates the potential for a pandemic, which is why we are acting quickly and aggressively."
But though there has been "no evidence of sustained community spread outside North America," Dr. Michael J. Ryan, the director of the WHO's global alert and response team, said today that he "would still propose that a pandemic is imminent, because we are seeing the disease spread."
WHO: 'Expect' Pandemic Alert Level to Rise
On Wednesday, the WHO upgraded the pandemic alert level to phase five, which "is a strong signal that a pandemic is imminent," according to the organization's guidelines. During the current phase, officials around the world have stepped up preparations for a potential pandemic and increased communication and coordination.
The next level, six, indicates that "a global pandemic is under way," the guidelines say.
"At this point we have to expect that phase six will be reached, we have to hope that it is not reached," Ryan said. But he added that the term pandemic only refers to the geographic spread of a disease, not its severity.
Ryan spoke at a briefing earlier today at the WHO headquarters in Geneva. He said the organization is dispersing 2.4 million courses of antiviral medication to 72 developing countries, including Mexico.
Obama said today that the United States will continue "investing in every resource necessary to treat this virus and prevent a wider outbreak."
"The good news is that the current strain of H1N1 can be defeated by a course of antiviral treatment that we already have on hand," he continued, adding that the nation's stockpile of such medicines had 50 million courses of treatment at the beginning of the week, and that a quarter of the medicine has been distributed to states.
"We then purchased an additional 13 million treatments to refill our strategic stockpile," Obama said. Additionally, he said that "out of an abundance of caution," he has asked Congress for $1.5 billion to be set aside for more medicines, supplies and the development of an H1N1 flu vaccine.
The CDC has confirmed cases in New York, Texas, California, South Carolina, New Jersey, Arizona, Colorado, Connecticut, Delaware, Florida, Illinois, Indiana, Kansas, Kentucky, Massachusetts, Michigan, Minnesota, Missouri, Nevada, Virginia and Ohio.
Officials still remain cautious about the outbreak. Friday afternoon a United Airlines flight from Germany to Washington, D.C., was diverted to Boston after a passenger complained of flu-like symptoms.
Schools, Children and Swine Flu
The U.S. Department of Education said Friday that officials in 18 states ordered more than 430 schools closed, affecting an estimated 245,000 students.
In Brownsville, Texas, officials ordered the closing of the entire school district Friday, a move taken in several school districts around the country, including nearby Fort Worth.
Children, Schuchat said, take longer to shed viruses and other diseases, and often do so without symptoms. The majority of the swine flu cases in the United States have occurred in those younger than 20 years old. The median age of those with the disease is 17, though the ages range from 1 to 81, according to Schuchat.
Current CDC guidance suggests that schools with a confirmed or probable case of swine flu should consider closing for up to 14 days, "but with regular reevaluations of the circumstance."
"The goal" of social distancing efforts like school closures, Schuchat said, "is to try to decrease the ongoing numbers of cases and to shift them to a later time by slowing transmission."
A slowdown in the spread of the virus would give the government more time to develop a vaccine during the summer months, when conditions help slow the spread of disease, and into the fall.
U.S. authorities have promised to produce enough swine flu vaccine for the country, but it won't be available until fall at the earliest.
Health and Human Services Assistant Secretary Craig Vanderwagen told lawmakers that it would take several months before pilot tests on humans could ensure that any vaccine would be safe and effective against the flu. Assuming that everything goes well, mass production of the vaccine could begin in the fall.
"We think 600 million doses is achievable in a six-month time frame" from that fall start, he said, adding, "I don't want anybody to have false expectations. The science is challenging here."
Swine Flu Spreads, Stress Levels Soar
As the flu spreads, stress levels have soared nationwide. U.S. prescriptions for anti-viral flu medications spiked this week, increasing almost 900 percent, according to prescription tracker SDI.
Los Angeles saw the most dramatic increase of any U.S. city, with doctors writing an average of 16 times more prescriptions than their daily average.
Signs of concern abound. Most major U.S. airlines announced Friday that they will temporarily cut back on flights to Mexico to match weak demand. Religious organizations are altering their services this weekend, avoiding activities that call for close contact between congregants. Some churches will not serve communion wine or place wafers in the mouths of congregants because of the risk of swine flu.
But others are looking to profit on the fear. In Indiana, state officials warned of swine flu telephone scams, in which someone pretending to be from the CDC calls offering "mandatory swine flu kits."
Meanwhile, U.S. public health officials are continuing to watch the disease's spread and develop plans for response.
"We continue to ask the question about how severe this particular strain of H1N1 influenza virus is and will evolve to be here in the U.S.," Schuchat said.
The Associated Press and Reuters contributed to this report.