Norovirus, influenza explained

“We’re not happy until you’re not happy!” This could be the mantra of two common viruses – norovirus and influenza viruses.

Although they are not related, these two viruses are the culprits for a lot of the misery association with “stomach flu” and “the flu.” Let’s take a look at the differences between these two common viruses.

Norovirus causes “stomach flu,” which is actually a misnomer and should be called acute gastroenteritis. As the name suggests, symptoms of gastroenteritis include vomiting, diarrhea and abdominal cramping. Not a pretty picture and, for those who suffer through gastroenteritis, not a pleasant experience.

Norovirus spreads through contaminated food or water or by contact with contaminated surfaces. It can survive in ice cubes. There is no treatment and no vaccine, and most people will recover in a few days.

Cruise ships were the main locations of norovirus outbreaks. Over the past five years, an average of about 14 cruise ships a year has had outbreaks of diarrheal illness. In 2014, Royal Caribbean’s Explorer of the Seas had more than 600 passengers and crew members sick with gastroenteritis. The Princess Cruise’s Caribbean Princess arrived in a different port the same day after an outbreak sickened at least 192 people aboard.

But things have changed. Norovirus infects 20 million Americans a year, according to the Centers for Disease Control and Prevention, thriving in closed areas like dormitories, summer camp cabins, health care facilities and other places, in addition to cruise ships.

In recent years on Maui, norovirus outbreaks have been investigated at long-term-care facilities, schools and even shopping centers. These outbreaks are becoming common.

Unlike the relatively benign norovirus, the viruses that cause influenza, which kills thousands of people every year in the U.S., is hardly benign. Most of the deaths from seasonal influenza (flu for short) are the very young and the elderly. According to the World Health Organization, the flu kills an estimated 250,000 to 500,000 people worldwide every year.

Influenza viruses are something most people will contract during their lives because they are easily spread from person to person. Certain strains of flu viruses are deadlier than others. The 2009 H1N1 strain attacked all ages but caused a higher proportion of deaths in younger, healthier adults than the common circulating viruses. The emergence of the 2009 H1N1 strain signaled the first pandemic flu of the 21st century.

The 2009 H1N1 strain is still with us, and is one of the circulating strains of flu viruses. Fortunately, one of the viruses used to make the 2013-14 trivalent flu vaccine is the H1N1 virus. As a reminder, it normally takes two weeks after vaccination for the body to produce protective antibodies.

The predominant influenza viruses in circulation may change year to year, which makes it difficult to develop a vaccine that provides a good match to all viruses. A universal flu vaccine, which would protect against all strains of influenza viruses, is being tested and hopefully will be developed in the near future.

One very important difference between norovirus and influenza viruses is that alcohol-based hand sanitizers do not kill norovirus. In fact, this might contribute to the spread of norovirus by lulling people who use alcohol-based hand gels religiously into a false sense of security. Hand-washing is the most effective means of removing both of these viruses from your hands.

Lastly, one of the big problems with both of these viruses: Influenza viruses can spread after a person’s symptoms subside while victims who recover from norovirus can still spread the virus to others for another two to three days after the symptoms are gone. You may want to rest and recover by staying home a couple more days rather than sharing the germs with others. Your peers will thank you for your consideration.

* Marc Nishimoto is the public health preparedness planner for the Maui District Health Office.