Health officials told lawmakers Wednesday it took only two weeks to identify the genetic characteristics of swine flu, and they are in good position to quickly produce a vaccine if the flu takes a turn for the worse.
At the same time, the officials cautioned members of a House Foreign Affairs subcommittee that there are still elements of what they called the novel 2009 H1N1 influenza virus that they don't understand, and it was not time for complacency.
"We have isolated and identified the virus and discussions are under way so that, should we need to manufacture a vaccine, we can work towards that goal very quickly," Dr. Anne Schuchat, acting deputy director for science and program at the Centers for Disease Control and Prevention told a U.S. House hearing.
Dr. Dennis Carroll, a special adviser on pandemics with the U.S. Agency for International Development, said investments to stave off an avian flu epidemic helped lay the groundwork for the quick response to swine flu.
VIDEO: How to Prevent the Spread of Swine Flu
The virus continues to set off health alarms. A Texas woman with the H1N1 flu virus died early Tuesday after being hospitalized since April 19, state health officials said, the second death outside of Mexico.
Officials identified the woman as a 33-year-old pregnant schoolteacher who fell into a coma and had her baby delivered by Caesarean section. State health department spokeswoman Carrie Williams said Judy Trunnell had "chronic underlying health conditions" but wouldn't give any more details.
U.S. health officials have predicted that the swine flu virus would spread and inevitably kill some people, just as seasonal flu does. Last week a Mexican toddler visiting Texas also died.
Mexico announced Wednesday a jump in the confirmed death toll to 42 after testing backlogged cases. It also confirmed 1,070 other cases of infection.
Two of those deaths were from Tuesday, and there have been six since May 1. While the rate of new cases and hospitalizations has declined, epidemiologists said the virus has spread throughout Mexico.
"We have seen a tendency (of the outbreak) to diminish, but not disappear," Health Secretary Jose Angel Cordova said.
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The bulk of these remain in North America.
The United States has more than 600 confirmed cases in 41 states, the CDC said, with another 700 "probable" cases. Canada has reported 165 cases.
Pandemic Alert Remains
For health authorities worldwide, the question remained how far the virus would spread and how serious would it be. The WHO remained at pandemic alert level 5, meaning a pandemic is imminent.
"If it spreads around the world you will see hundreds of millions of people get infected," the WHO's Dr. Keiji Fukuda told a news briefing.
If it continues to spread outside the Americas, the WHO would likely move to phase 6, a full pandemic alert. This would prompt countries to activate pandemic plans, distribute antiviral drugs and antibiotics and perhaps advise people to take other precautions like limiting large gatherings.
"It's not so much the number of countries, but whether the virus sets up shop in any of those countries like it has here and starts to spread person to person. And given the number of countries that have cases, one would think that eventually that criteria would be met," said acting CDC director Dr. Richard Besser.
He and Fukuda said it would be important to watch the Southern Hemisphere, where winter and the flu season are just beginning.
Other pandemics have started with a mild new virus in spring that has come back to cause severe disease later in the year. WHO said it would begin sending 2.4 million treatment courses of Roche AG's and Gilead Sciences Inc's Tamiflu, an antiviral proven effective against the new flu, to 72 nations.
Mexicans, Canadians Head Home
Dozens of Mexican nationals quarantined in China despite having no swine flu symptoms arrived home Wednesday on a government-chartered jet, some complaining of "humiliation and discrimination" by the Chinese.
First lady Margarita Zavala was up before dawn to greet the 136 passengers at Mexico City's international airport. Authorities said 72 had been in Shanghai, 18 in Beijing, 34 in Guangzhou and 12 in Hong Kong. None had flu symptoms, Mexican diplomats said.
Several other Mexican passengers said they were treated well despite being quarantined for four days.
China also released a group of Canadian students from swine flu quarantine on Wednesday, while dozens more people isolated on the mainland and in Hong Kong were expected to regain their freedom soon.
The group of 25 students and a professor from a Canadian university had been under "observation" at a hotel in the northeastern Chinese city of Changchun since the weekend but were released Wednesday instead of Friday because they were healthy, provincial health official Lin Ji said.
Canada questioned why they needed to be isolated immediately upon their arrival in Changchun on Saturday, given that none exhibited symptoms of the virus.
China defended its measures to block the swine flu virus from entering the world's most populous nation. The quarantines have also ensnared several American travelers.
The Associated Press and Reuters contributed to this report.
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