April 28: Robert Nickla prepares clinical samples submitted for influenza testing at the Arizona State Laboratory in Phoenix.
April 27: Men wear masks as they depart the customs area Monday at San Francisco international airport.
Apr. 29: Doctors look at the charts of a patient who is suspected of having swine flu at a hospital in Oaxaca, Mexico.
April 29, 2009: Wearing a protective face mask, a woman and her child leave the emergency area of a hospital in Mexico City.
April 28, 2009: A nurse shows how to perform a test for swine flu virus with her colleague at the Malmo Academic Hospital in Malmo, Sweden.
April 28, 2009: Passengers wear protective masks as they ride Mexico's city subway.
April 25: Hiram Diaz, 8, left, gives his 6-year-old sister Adely Diaz a ride on the pegs of his bicycle while wearing protective masks in Mexico City.
Mexico's top epidemiologist says the World Health Organization was slow to react to an outbreak of atypical pneumonia that grew into the swine flu epidemic, and wants a probe.
In a telephone interview with The Associated Press, Dr. Miguel Angel Lezana says he is troubled by the response of the Pan American Health Organization, or PAHO, and its parent organization, the WHO, in the early days of the outbreak.
Lezana, director of the National Epidemiology Center, says it notified PAHO on April 16 about the outbreak in Mexico, but that action wasn't taken until eight days later, when the WHO announced the spreading epidemic..
Experts, however, are asking whether the health system in Mexico is up to dealing with the outbreak and whether an earlier response might have prevented its worldwide spread.
"Mexico does not have the kind of measures in place we have in this country," said Dr. Len Horovitz, a pulmonary specialist at Lenox Hill Hospital in New York. "This virus has been circulating since sometime in March and could involve thousands or hundreds of thousands of people."
Reports indicate that hospitals around Mexico started seeing a rise in patients complaining of respiratory distress as early as the middle of last month.
But the WHO wasn't made aware of the situation until a month later. Within a week people in Mexico were dying of flu-like symptoms and two children in California were diagnosed with a new strain of swine flu, believed to be the same strain circulating through Mexico.
Dr. Keiji Fukuda, an assistant director general with the WHO, defended Mexican health officials in a news conference on Sunday, pointing out that the country — which has been hard hit by the global recession and is devoting many of its resources to its war against drug cartels — was in the middle of flu season when the increase in patient load began.
Mexico's top medical officer voiced optimism Thursday that swine flu has slowed in the nation hardest hit by the virus, but the World Health Organization cautioned there is no evidence the worst of the global outbreak is over.
The U.S. caseload rose slightly to 130 as hundreds of schools nationwide shut their doors, and the crisis even reached the White House, which said an aide to the secretary of energy apparently got sick helping arrange a presidential trip to Mexico.
Mexican health authorities said Thursday they confirmed 300 swine flu cases and 12 deaths due to the virus among a total of 679 people tested so far.
Less than half of the suspected cases tested have been confirmed as swine flu, and a series of visits to the families of victims also turned up relatively few suspected cases.
Authorities had previously listed 260 confirmed cases, and said the number of cases appeared to be stabilizing.
Health Secretary Jose Cordova said one encouraging sign was that the daily number of people admitted to government-run Social Security hospitals with swine flu symptoms had fallen from a high of 212 people on April 20 to 46 on Thursday.
Health workers have so far visited the homes of 77 suspected victims and found only two cases in which relatives tested positive for an A-type flu virus that could be related to the swine strain.
Cordova said Thursday that authorities had approved or spent 1.6 billion pesos ($116 million) for medical supplies and equipment so far in the epidemic.
Where Did Virus Originate?
Medical detectives have not pinpointed where the outbreak began. Scientists believe that somewhere in the world, months or even a year ago, a pig virus jumped to a human and mutated, and has been spreading between humans ever since.
China has gone on a rhetorical offensive to squash any suggestion it's the source of the swine flu after some Mexican officials were quoted in media reports in the past week saying the virus came from Asia and the governor of Mexico's Veracruz state was quoted as saying the virus specifically came from China.
One of the deaths in Mexico directly attributed to swine flu was that of a Bangladeshi immigrant, said Mexico's chief epidemiologist Miguel Angel Lezana.
Lezana said the unnamed Bangladeshi had lived in Mexico for six months and was recently visited by a brother who arrived from Bangladesh or Pakistan and was reportedly ill. The brother has left Mexico and his whereabouts are unknown, Lezana said. He suggested the brother could have brought the virus from Pakistan or Bangladesh.
By March 9, the first symptoms were showing up in the Mexican state of Veracruz, where pig farming is a key industry in mountain hamlets and where small clinics provide the only health care.
The earliest confirmed case was there: a 5-year-old boy who was one of hundreds of people in the town of La Gloria whose flu symptoms left them struggling to breathe.
Neighbors of the inspector, Maria Adela Gutierrez, said Wednesday that she fell ill after pairing up with a temporary worker from Veracruz who seemed to have a very bad cold. Other people from La Gloria kept going to jobs in Mexico City despite their illnesses, and could have infected people in the capital.
There is no vaccine to prevent infection but U.S. health officials aim to have a key ingredient for one ready in early May, the big step that vaccine manufacturers are awaiting. But even if the World Health Organization ordered up emergency vaccine supplies — and that decision hasn't been made yet — it would take at least two more months to produce the initial shots needed for human safety testing.
"We're working together at 100 miles an hour to get material that will be useful," Dr. Jesse Goodman, who oversees the Food and Drug Administration's swine flu work, told The Associated Press.
Obama asked Congress for $1.5 billion in emergency funds to help build more drug stockpiles and monitor future cases, as well as help international efforts to avoid a full-fledged pandemic.
Obama said his administration has made sure that needed medical supplies are on hand and he praised the Bush administration for stockpiling 50 million doses of antiviral medications
Swine Flu vs. Seasonal Influenza
“The illness is consistent with seasonal influenza and has generally the same symptoms of seasonal influenza,” Fukuda said. “Our information to date shows that the infection can range from very mild, requiring no hospitalization and recovering after a few days, to fatal, which is also in keeping with seasonal influenza."
Fukuda said there is no evidence that the virus is spreading from pigs or that it is unsafe to eat pork.
Authorities sought to keep the crisis in context: Flu deaths are common around the world. In the U.S. alone, the CDC says about 36,000 people a year die of flu-related causes.
Children, especially those younger than age 5, are particularly vulnerable to flu and its complications, and every year children die from seasonal flu.
According to the CDC, more than 20,000 children younger than age 5 are hospitalized every year because of seasonal flu. In the 2007-08 flu season, the CDC received reports that 86 children nationwide died from flu complications.
As of April 11, CDC had received reports of 53 seasonal flu-related deaths in children during the current seasonal flu season.
Still, the CDC calls the new strain a combination of pig, bird and human viruses for which people may have limited natural immunity.
Hence the need for a vaccine.
The Associated Press and Reuters contributed to this report.