The United States is currently in the grip of three separate epidemics.  According to, influenza, whooping cough and norovirus --a stomach virus that causes diarrhea, vomiting and cramping -- are all currently storming through the population, and some experts warn that the flu season is just getting started and will only get worse from here. explained that the flu epidemic is particularly bad this year because the main strain circulating, influenza A (H3N2), is a nasty one.  Flu seasons caused by influenza A tend to have a higher number of hospitalizations and deaths than other strains.

Also, this year flu season started early, in the first week of December rather than the fist week of January as it normally does.  It was the earliest start to a flu season since winter of 2003-2004.

Twenty-nine states and New York City are reporting higher than average levels of flu activity.  CNN reported on Friday that 18 children have died already this flu season, and the U.S. is still at the early stages of the year's outbreak.

Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases at the National Institutes of Health, told CNN on Thursday that the country is in the midst of a full-blown epidemic, but that the disease is "still on the uptick."

While flu seasons are unpredictable, Fauci said that this is currently week five of what should be a 12-week epidemic.

"Remember, once it peaks, you still have a considerable amount of time where there is a lot of flu activity, and right now it may have peaked in some places, but for the most part, it has not yet peaked," he said.

On Wednesday, Boston Mayor Thomas Menino declared a public health emergency in his city.  Since October 1, there have been 700 confirmed flu cases in Boston, ten times more than the city saw in all of last year's flu season.  Thus far, 18 people have died.

Whooping cough, or pertussis, has been on the comeback in recent years, thanks to a combination of factors. Currently the U.S. is seeing the worst outbreak of pertussis since 1955. Partly to blame are parents who have chosen to forego their children's immunizations on ideological grounds or for health reasons.  Another factor is believed to be the type of pertussis vaccine used in this country since 1997, a purified version of the vaccine that was thought to be safer for children, but has turned out to confer immunity to the disease for a shorter time.

Dr. Paul Offit, the chief of the Division of Infectious Diseases  at the Children's Hospital of Philadelphia, said that while it's unfortunate to see a once-vanquished childhood killer rear its head in the population, higher numbers of people will develop immunity naturally from having been exposed.  After this year, he predicted, the number of cases will go back down.

Norovirus, also known as the "cruise ship virus" or by its British name, "winter vomiting disease," is also spreading wildly throughout the country.  Offit said this year's cases are unusual because the disease is flaring up in multiple locations at once, rather than being confined to a specific area.

Some scientists call norovirus "the Ferrari of the virus world" in that it's "one of the most infectious viruses known to man."  The virus causes patients to become miserably ill with stomach cramps, nausea, diarrhea and (sometimes violent, projectile) vomiting.

The CDC says that each year, norovirus will sicken some 21 million people in the United States, causing around 700,000 hospitalizations and some 800 deaths.  In the U.K., norovirus infections are up 63 percent over this time last year.

To make matters worse, a new strain of norovirus, named Sydney 2012, has emerged this year. Britain's Health Protection Agency (HPA) said that genetic testing has proven that the new strain is responsible for the majority of cases in that country this year, and warned that patients in the U.S. and around the world could soon follow suit.

None of these diseases are related to the others, warn health experts, they just all happen to be circulating simultaneously.  The CDC recommends getting a flu shot and making sure children are up to date on their vaccinations.  The health organization also recommends normal flu season precautions like avoiding contact with people who are sick, coughing and sneezing into the crook of the arm rather than the hands, as well as frequent hand-washing.

Watch video about this year's flu epidemic, embedded below via CNN:

[image via Shutterstock]