( CNN ) -- With mostly mild cases of swine flu in the United States , swine flu fears are lessening . But viruses have a way of re-appearing . While nobody has a crystal ball , here are some thoughts about what the 2009 H1N1 virus might do in the months to come . Do n't pack your face masks just yet . Public health officials expect the 2009 H1N1 virus to linger a while . 1 . Is the swine flu outbreak in the United States winding down ? Not yet . Health officials expect to see more cases . However , there are two reasons to think the 2009 H1N1 outbreak will wind down in the coming weeks . First , cases of influenza tend to dwindle when the weather gets warmer . Second , the 2009 H1N1 virus outbreak in Mexico has reached its peak , and numbers there are going down . It is expected that same pattern could happen in the United States . For the latest information from the Centers for Disease Control and Prevention , click here . Look at a map of swine flu cases » . 2 . So does this mean 2009 H1N1 will be gone for good ? No . Andrew Pekosz , associate professor of immunology and microbiology at Johns Hopkins University Bloomberg School of Public Health , says it 's important to keep in mind that the 2009 H1N1 virus is new , which means no one has immunity to it . He points out that the three outbreaks in the last century that were caused by new viruses -- in 1918 , 1957 and 1968 -- started with a mild wave followed by more severe waves months later . Scientists dig for lessons from past pandemics . 3 . If swine flu comes back , when would it return ? `` H1N1 flu could die down soon and return later again this fall when the flu season enters back in full swing , '' says Secretary of Homeland Security Janet Napolitano . `` This is always a concern with a new strain of a flu virus . '' Watch more answers to your swine flu questions » . Napolitano adds that public health officials will be keeping a close eye on the Southern Hemisphere , where flu season starts soon . `` We 'll be working very closely with the international community to understand what happens to this virus over the next few months as flu season begins in the Southern Hemisphere , '' she says . `` That will tell us a lot about whether the virus is changing , whether it 's becoming more severe and what measures we might want to take in the fall . '' For the latest comments from Napolitano , click here . 4 . In the fall , could we have a pandemic like we had in 1918 ? At a press briefing last week , World Health Organization spokesman Gregory Hartl brought up the specter of the 1918 pandemic , which killed more than half a million people in the United States . `` In 1918 , that pandemic started out as a very mild case of disease in the spring of 1918 . ... Cases of the disease almost completely disappeared over the summer , only to reappear in the autumn of 1918 with the vengeance which we all know , '' he said . `` So even though we might be only seeing mild cases now , we can not say what will happen in the future . '' Learn more about the swine flu » . But many experts believe it 's highly unlikely there would be an outbreak anything like 1918 . First of all , scientists have a much better understanding of infectious diseases , and health care has improved greatly since 1918 . Secondly , the 2009 H1N1 lacks a gene that is present in highly virulent flu viruses , such as the one in 1918 . `` I do n't think this virus has what it takes to become a major problem , '' says Peter Palese , chairman of the department of microbiology at Mount Sinai School of Medicine in New York . Johns Hopkins ' Pekosz adds that people remember the horrific 1918 flu season , but often forget that the two other flu outbreaks caused by new viruses , the ones in 1957 and 1968 , were far more mild . 5 . Will there be a vaccine for swine flu ? Scientists are already working on a vaccine for 2009 H1N1 . Making a new vaccine takes five to six months , according to the World Health Organization . The first step is for government scientists to grow `` seed stock '' of the virus to send to pharmaceutical companies , who would turn that stock into a vaccine . Pilot lots of the vaccine would then be tested on people . The National Institute of Allergy and Infectious Diseases alerted its eight vaccine testing centers to be ready to test a 2009 H1N1 vaccine . 6 . Will the vaccine be a separate shot , or will it be put in the regular seasonal flu shot ? The Centers for Disease Control has said either is possible . Pekosz says there are concerns the seasonal flu shot might not work well if it includes the 2009 H1N1 vaccine , and so the decision might be made to make a separate shot . 7 . If a vaccine is available in the fall , who will get it ? Public health officials have emphasized that even if a vaccine is available by fall , it does n't mean everyone will be encouraged to get it . `` I imagine that the choice of vaccination strategy will be a subject of intense discussion and study over the next several months , '' says Dr. Ted Cohen , an assistant professor of epidemiology at the Harvard School of Public Health . Cohen adds that if the vaccine is available only in limited quantities , priority might be given to health care workers and to those at high risk of complications from the flu , such as the elderly , the very young and those with certain chronic diseases . CNN 's Jennifer Pifer Bixler and Shahreen Abedin contributed to this report .
Swine flu cases may have peaked , but the 1918 H1N1 virus will probably return . Public health officials to watch the Southern Hemisphere to see what 2009 H1N1 does . Scientists are working on a vaccine against 2009 H1N1 ; wo n't be ready for 2009 . 2009 New York lacks a gene that is present in very virulent flu viruses , like 2009 strain .