FRANK JORDANS Associated Press Writer GENEVA (AP) — The World Health Organization called a third emergency meeting in response to a spike in swine flu cases and said the expert panel will discuss Wednesday whether to raise the worldwide flu alert level. After the panel's first meeting Saturday, WHO declared the outbreak an international public health emergency and on Monday it raised the pandemic alert level from phase 3 to 4 to show that the risk of a global outbreak had increased. Level 4 is two levels below the top threshold — a full pandemic outbreak. "The director-general has seen a jump in cases and she wants to have that evaluated by the outside experts," WHO spokesman Dick Thompson said. WHO chief Dr. Margaret Chan will convene the emergency committee by teleconference after the global body holds a "scientific review" of the outbreak to determine exactly what is known about how the disease spreads, how it affects human health and how it can be treated. Swine flu is suspected of killing more than 150 people in Mexico and sickening over 2,400 there. WHO has confirmed 105 cases of swine flu in seven countries, but reports are still coming in. Over half of the confirmed cases — 66 — are in the United States. In an interview with CNN, Dr. Richard Besser, acting director of the U.S. Centers for Disease Control and Prevention, confirmed the flu death of a 23-month-old child in Texas — the first death outside Mexico. Wednesday's meeting does not necessarily mean that WHO will raise its pandemic alert level further, Thompson said. Raising the alert level to phase 5 would indicate the virus has become established in at least two countries, causing outbreaks among people who haven't traveled abroad. It could also trigger a recommendation from WHO for vaccine manufacturers to switch production from seasonal flu vaccines to a pandemic vaccine. It will take at least 4-6 months to get the first batches of a pandemic vaccine. Dr. Nikki Shindo, a WHO flu expert taking part in the scientific review, said medical experts are still trying to determine just how dangerous the virus is. "The one thing we don't really understand is why the cases in Mexico are so severe," she said, adding that WHO is looking into whether the Mexican cases involve underlying medical conditions that have caused people there to fare worse than patients elsewhere. Shindo told The Associated Press that "hundreds of thousands" of people in Mexico could theoretically be infected with swine flu even if they are showing no or only mild symptoms. The scientific review meeting will focus particularly on a large trove of data coming from Mexico, believed to be the epicenter of the virus, and from New York City, where a smaller outbreak has infected people. Shindo said the outbreak linked to students at St. Francis Preparatory school in Queens is an important case study that "will help us understand how the virus is spread, it's incubation period and the severity of infection." She said doctors expect to have a much fuller understanding of how the swine flu virus infects people by the end of the week. "The tricky thing is the virus will evolve very, very quickly, so we have to continuously monitor it," she said. "We have to receive sequential samples from cases and we have to exchange information among the countries that already have cases to monitor the change of the virus." In the past, most swine flu patients have shown only mild symptoms, and the disease tends to be far less serious in humans and animals than the bird flu virus that has infected at least 421 people and killed 257 in the last six years. Partly for that reason, much of the global preparations for a possible pandemic had focused on bird flu. Shindo said it was important to keep in mind that even normal flu outbreaks kill people. In poor countries such as Madagascar and Congo, outbreaks of seasonal influenza have infected up to half of the population, with mortality rates reaching 1 percent of the entire nation. Shindo said WHO affiliates around the world will also consider a request from the Food and Agriculture Organization to stop calling the disease swine flu, since the virus is not food-borne and has nothing to do with eating pork. U.S. Agriculture Secretary Tom Vilsack and others have suggested a new name, arguing that swine flu suggests a problem with pork products. China, Russia and Ukraine are among the countries who have banned pork imports from Mexico and parts of the United States affected by swine flu.