What is it? H1N1 is a new Influenza A virus first detected in the United States in April 2009. This virus is spreading from person-to-person, probably like other seasonal influenza viruses spread. We do not yet know how easily it spreads between people.

Why call it Swine Flu? This was originally called “Swine flu” because of initial laboratory testing, but subsequent study reveals that this new virus is very different from that which normally circulates in North American pigs. In this H1N1 variant, there are avian genes, human genes and two genes from pig flu viruses. This is termed a “quadruple reassortant” virus.

How bad is it? Like seasonal flu, H1N1 flu in humans varies in severity. Only the vast minority of cases result in death. In the US, the case fatality rate is 1.3 per 1000 (see below).

What are the symptoms? Symptoms of H1N1 flu are similar to the normal seasonal flu symptoms, including fever, body aches, sore throat, chills, fatigue, headache and cough. The current H1N1 flu may also produce vomiting and diarrhea. Symptoms in adults that warrant urgent medical attention include: difficulty breathing, shortness of breath, confusion, chest or abdominal pain, sudden dizziness, severe or persistent vomiting, or recurrence of fever that had abated. In children, look for these as well as: bluish or gray skin discoloration, severe lethargy or irritability, or insufficient fluid intake.

What is the treatment? There are four antiviral medications currently available in the US (by prescription only) for the prevention and treatment of Influenza A. The efficacy requires early initiation of therapy, generally within the first 24 hours of onset, and definitely within the first 48 hours. There are two M2 inhibitors, effective against Influenza A only: Amantidine (trade name Symmetrel) and Rimantidine (Flumadine). The two others, neuraminidase inhibitors, are effective against both Influenza A and Influenza B- Zanamivir (Relenza) and Oseltamivir (Tamiflu). Current recommendations suggest that the H1N1 variant is only sensitive to the neuraminidase inhibitors. Other treatment is supportive, such as rest, fluids, and acetaminophen (Tylenol) or ibuprofen (Advil).

Current US cases? As of today (May 22, 2009), there have been 6,552 confirmed or probable cases and 9 deaths (mostly in individuals with other concurrent medical issues) in the US from H1N1 flu. Texas leads the cases with 900, followed closely by Illinois with 877. Other states with more than 400 cases include: Arizona (520), California (553), Washington (494) and Wisconsin (766). Three of the nine deaths were in Texas. Only Alaska, Wyoming, and West Virginia have no confirmed cases (yet).