This year, it’s come with a vengeance.

With numbers of cases in many areas surpassing those of the 2009-10 swine flu pandemic, this year’s flu is emptying workplaces and crowding hospitals all over the country.

Each year, the flu strain varies, a reality that makes the annual, advance preparation of vaccine difficult. In most recent years, the predominant strain has been H1N1, but this year, it is H3N2, which is more aggressive and, in past years (i.e., 2003-04), relatively more fatal.

Something Other Than Flu…

If your symptoms are mostly vomiting and diarrhea, you probably have norovirus, not the flu.

According to the CDC, this year’s norovirus strain is one of the worst in years, and it has spread rapidly across the U.S. Fifty-eight percent of victims who report “stomach flu” actually have norovirus. The worst symptoms usually come on quickly and pass within one to three days. It is easily transmittable and has no effective treatment. The main danger is dehydration (small children and the elderly are particularly susceptible). Drink plenty of liquids. If your child’s vomiting or diarrhea is severe, provide oral rehydration solution to avoid dehydration.

According to the CDC, this year’s vaccine is well-matched to the H3N2 strain, and cases of H1N1 have been rare. With a third strain – B – targeted in this year’s vaccine, it is about 70 percent effective, due to the fact that it was formulated for only one of two B strains that are circulating (in next year’s vaccine, both B strains will be targeted). In Canada, the vaccine is judged to be about 47 percent effective.

The H3N2 strain is not resistant to Tamiflu, a prescription antiviral liquid or pill that can minimize symptoms and speed healing if it is administered within the first 48 hours of illness. Relenza, another antiviral drug, comes in powdered form (and is not suitable for patients with breathing problems). Generally, these drugs are reserved for patients who are hospitalized or at risk for serious complications (young children, the elderly, pregnant women and those with chronic illnesses).

If you have not gotten a flu shot, you should do so immediately. Other than Tamiflu and Relenza, flu has no effective drug treatments. If you do get the flu, you have no choice but to rest and let it run its course (typically three to five days).

If you become ill, you should stay at home. Do not go out or to work where you will spread the disease to others.

The best way to avoid the flu in the first place is to avoid contact with infected people and with surfaces that may be contaminated. Information on the benefits of soap and water and hand sanitizers is available here. If you are using a hand sanitizer, it should be 60% alcohol to be effective. You can help avoid spreading disease by covering your mouth and nose when sneezing or coughing and washing your hands regularly.

This year’s flu outbreak is complicated by the simultaneous spread of two other diseases with similar symptoms. One is a norovirus, known as the “cruise ship flu” or “stomach flu,” which includes a new strain, the Sydney 2012 variant (it first appeared last year in Australia). The classic symptoms are “explosive” diarrhea and “projectile” vomiting. Such symptoms can lead rapidly to dehydration and should be watched carefully.

In addition, this year’s flu pandemic is accompanied by the largest outbreak of pertussis since 1955. Pertussis (whooping cough) is unrelated to flu but causes hacking, coughing and breathlessness. The greatest danger is to infants; 15 of 18 recorded deaths in 2012 were among infants under one year of age. The outbreak is worst in cold-weather states, including Colorado, Washington, Wisconsin, Minnesota and Vermont. Typically, children are vaccinated against pertussis, but the protection of a new vaccine, introduced in the 1990s, appears to wear out more quickly than previous (but less safe) versions. It is thought that more teenagers and young adults may be vulnerable.

Flu symptoms may be similar to those of a bad cold, but a high fever, aches, chills and fatigue are more common and severe with flu. Below are resources for more information:

WebMD

FamilyDoctor.org

Centers for Disease Control

[Steve Clark]