Number of confirmed H1N1 cases worldwide soars

GENEVA, Switzerland (CNN) -- Confirmed cases of swine flu jumped by more than 65 percent Saturday with the World Health Organization reporting 615 people in 15 countries infected with the virus commonly known as swine flu. A policeman guards a Hong Kong hotel where 300 people are under quarantine. A policeman guards a Hong Kong hotel where 300 people are under quarantine. Click to view previous image 1 of 2 Click to view next image more photos » The organization had reported 367 cases on Friday. The jump in cases was due to ongoing testing of a backlog of specimens in Mexico, the WHO said. The most cases were in Mexico, where 397 people were infected and 16 deaths were attributed to the virus, according to the WHO. Next was the United States, which has 141 cases and one death. "What the increase reflects is that we are moving forward in confirming many of the cases that have been left untested for some time, so in an way that's reassuring," said WHO spokesman Paul Garwood. "We know that these cases are being dealt with, these specimens are being looked at and assessed, and we're getting more and more info about this virus. Video Watch latest developments as swine flu sweeps world » "So we haven't seen, say, a spike in new cases or new influenza cases appearing in Mexico City, for example," Garwood continued. "It's just the fact that this reporting backlog is bearing fruit and we're seeing the results of that." The latest developments come as parts of Asia discovered they were not immune to the spread of the virus. Learn about the virus » Hundreds of guests and staff were under quarantine in China on Saturday after health officials determined that a hotel guest had contracted the H1N1 virus. Nearly 200 hotel guests and 100 staff members were ordered to stay in Metro Park Hotel in Hong Kong for seven days to stop the spread of the H1N1 virus, a government spokesman said. Read more about quarantined hotel guests The quarantine was ordered after a 25 -year-old Mexican man stayed in the hotel and became sick, according to the spokesman. It is the first confirmed case of the virus in Hong Kong, local medical officials said. Don't Miss * Hundreds isolated in Hong Kong hotel * Mexico trip costs students graduation * Dr. Sanjay Gupta 'tweets' on swine flu South Korean officials on Saturday confirmed their first case -- a 51-year-old nun who recently traveled to Mexico for volunteer work. The other countries with confirmed cases are Canada, with 34; Spain and the United Kingdom, which each have 13; Germany and New Zealand, which each have four; Israel, with two; and Austria, China, Denmark, France, the Netherlands, South Korea, and Switzerland, which each have one. See where cases have been confirmed » As the number of swine flu cases across the globe is expected to rise, scientists are racing to develop a vaccine to confront the virus. The Centers for Disease Control and Prevention in Atlanta, Georgia, hopes to have a vaccine for the virus available to manufacturers within a month, said Michael Shaw, the U.S. agency's lab team leader for the virus response. "We're doing the best we can as fast as we can," he said. Still, it would take four to six months from the time the appropriate strain is identified before the first doses become available, said Dr. Marie-Paule Kieny, WHO director of the Initiative for Vaccine Research. "Of course, we would like to have a vaccine tomorrow. We would have wanted to have it yesterday," she said. "It's a long journey." Kieny said there is "no doubt" that a vaccine can be made "in a relatively short period of time." Producing a vaccine involves isolating a strain of the virus, which has already been done, and tweaking it so manufacturers can make a vaccine, Kieny said. Video Go behind the scenes at the CDC » As researchers work, the mayor of Mexico City expressed optimism Friday. Authorities in Mexico are "beginning to see evidence that the (virus) might be letting up, and the number of people who have been hospitalized has leveled out in regards to people who are contagious, at least as of yesterday," Mayor Marcelo Ebrard told reporters. "I do not say this so that we lower our guard or so that we think that we do not have a problem anymore," he said. "We do have a problem, but I say this so that we know where we are as a city after we have done all we have done, and in what direction we are heading and how much we have progressed. And what I can say is that we are heading in the right direction." One death in the United States has been attributed to swine flu -- a toddler from Mexico whose family brought him to Texas for medical treatment. At a Cabinet meeting Friday, President Barack Obama praised the "extraordinary" government response to the virus but emphasized that "we also need to prepare for the long term." advertisement "Since we know that these kinds of threats can emerge at any moment, even if it turns out that the H1N1 is relatively mild on the front end, it could come back in a more virulent form during the actual flu season, and that's why we are investing in our public health infrastructure."