As an expert in the field of epidemiology and infectious diseases, I can provide you with a comprehensive answer regarding the possibility of getting the swine flu, also known as the H1N1 influenza virus, twice.

Influenza viruses are known for their ability to mutate and adapt, which is why they are responsible for seasonal flu outbreaks and occasional pandemics. The H1N1 virus, which caused the global pandemic in 2009, is no exception. It is a type of influenza A virus that primarily affects the respiratory system.

When you contract an influenza virus, your immune system responds by producing antibodies that are specific to the virus. These antibodies help to neutralize the virus and protect you from future infections by the same strain. This is known as immunity. However, the immune response to influenza viruses is not always as robust or long-lasting as we would like it to be.

The key factor that complicates the immune response to influenza is antigen drift. This is a process by which the virus undergoes small genetic changes over time. These changes can alter the structure of the virus's surface proteins, specifically the hemagglutinin (H) and neuraminidase (N) antigens, which are the targets of the immune system's antibodies. When these antigens drift enough, the immune system may no longer recognize the virus, and you can become susceptible to infection again.

Another factor is antigen shift, which is a more dramatic change in the virus's genetic makeup. This can lead to the emergence of a completely new strain of the virus, to which the population has little to no immunity. This is what happened in 2009 with the H1N1 pandemic.

Now, regarding the question of whether you can get the swine flu twice, the answer is technically yes, but it is not a straightforward process. If you are infected with the exact same strain of the H1N1 virus, the immunity developed from the first infection should protect you from a second infection by that same strain. However, if the virus undergoes antigenic drift or if a new strain emerges through antigenic shift, your immunity may not be as effective, and you could potentially be infected again.

It is also important to note that the immune system's memory can fade over time. This means that even if you have been infected with a particular strain of the virus in the past, your protection against it may decrease after several years.

In conclusion, while it is not common to be infected with the identical influenza virus more than once, it is not impossible due to the dynamic nature of these viruses and the limitations of our immune response. Vaccination remains one of the most effective ways to prevent infection and reduce the severity of illness if infection does occur.

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Getting infected with any influenza virus, including 2009 H1N1, should cause your body to develop immune resistance to that virus so it's not likely that a person would be infected with the identical influenza virus more than once. ... More information about flu diagnosis is available.Feb 10, 2010read more >>