GENEVA, Switzerland (CNN) -- The number of confirmed swine flu cases across the globe kept rising Friday, but some signs of hope emerged in the battle against the worldwide outbreak.



Tourists sunbathe wearing surgical masks in the popular Mexican resort of Acapulco.



The World Health Organization said Friday that the number of confirmed cases stood at 367 worldwide, including 141 in the United States and 156 in Mexico. Thirteen countries have confirmed cases, the organization said.



Meanwhile, researchers worked to develop a vaccine for swine flu, which is also known as 2009 H1N1.



The Centers for Disease Control and Prevention hopes to have a vaccine to manufacturers within a month, said Michael Shaw, lab team leader for the H1N1 response at the CDC.



"We're doing the best we can as fast as we can," he said.



Yet 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."



She said there is "no doubt" that a vaccine can be made "in a relatively short period of time."



The steps involved in producing a vaccine involve isolating a strain of the virus, which has already been done, and tweaking it so manufacturers can make a vaccine, Kieny said.



The tweaked virus will be shipped to manufacturers, who will fine-tune it. Then come more tests before national regulatory agencies decide whether to approve a vaccine.



As researchers work, at least one politician at the epicenter of the outbreak 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," Mexico City Mayor Marcelo Ebrard told reporters.  Watch how Mexican authorities are dealing with the outbreak »



"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."



The WHO said Mexico has 156 confirmed cases and nine deaths. Mexican authorities say they have confirmed 16 deaths and at least 358 cases, and they suspect more than 150 deaths may have been caused by the flu.  Watch Dr. Sanjay Gupta demystify pandemics »



The CDC gave the following state-by-state breakdown of the 141 confirmed H1N1 cases in the United States: Arizona, 4; California, 13; Colorado, 2; Delaware, 4; Illinois, 3; Indiana, 3; Kansas, 2; Kentucky, 1; Massachusetts, 2; Michigan, 2; Minnesota, 1; Nebraska, 1; Nevada, 1; New Jersey, 5; New York, 50; Ohio, 1; South Carolina, 16; Texas, 28; and Virginia, 2.  See where cases have been confirmed »



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.



In a Cabinet meeting, President Obama on Friday praised the "extraordinary" government response to the virus but emphasized that "we also need to prepare for the long term."



"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."  Go behind the scenes at the CDC »



He said there are indications from Mexico that "relatively young, healthy people" have died rather than people whose immune systems are compromised, and "that's why
Who says 16 people have died from virus? How many people died from the virus? How many people have died from the virus? How many countries did the virus spread to?
World Health Organization 16 deaths 150 deaths Thirteen
question: Who says 16 people have died from virus?, answer: World Health Organization | question: How many people died from the virus?, answer: 16 deaths | question: How many people have died from the virus?, answer: 150 deaths | question: How many countries did the virus spread to?, answer: Thirteen