With central Ohio already battling an extended season of shigellosis and influenza, health officials face a new threat: an outbreak of norovirus, which usually occurs during the winter months.
Infection rates for the highly contagious gastrointestinal disease are steady compared to previous years in central Ohio, said Jose Rodriguez, spokesman for Columbus Public Health.
But a new strain -- GII.4 Sidney -- has caused the majority of illnesses since fall, according to the Centers for Disease Control and Prevention.
Norovirus is easily transmitted by eating food or drinking from the same glass as someone who's been infected, touching contaminated surfaces and putting one's hand or fingers in one's mouth, or having direct contact with someone who's contracted the virus.
Commonly referred to as the stomach flu -- although influenza is a respiratory infection -- norovirus symptoms include vomiting, diarrhea and stomach cramps. The duration of the illness is 12 to 60 hours.
Individual cases aren't reported to Columbus Public Health. However, in the event of an outbreak, the agency will investigate, said Dr. Mysheika Williams Roberts, assistant health commissioner with the agency.
There have been three outbreaks this season: two in November involving 62 people, and another in December in which 31 people were infected.
If the outbreak is traced to a food source -- a restaurant, purveyor or caterer, for example -- health officials will ask for voluntary testing, Roberts said.
In the case of infection, workers must have two negative tests before they're allowed back to work, she said.
Because the symptoms are usually similar, it is often confused with food poisoning, which is caused by foodborne pathogens, Roberts said.
It sometimes results in hospitalization for people, mostly the elderly and young, who experience severe dehydration, she said.
A vaccine has proved elusive for several reasons, because there are several different types of noroviruses, said Dr. Dennis Cunningham, epidemiologist at Nationwide Children's Hospital.
The good news is that better testing has identified norovirus as a major problem, Cunningham said.
Also, there are two companies in Europe testing norovirus vaccines, but they have yet to go through the regulatory process, he said.
As is the case with influenza, prevention is the key.
Health officials urge people to wash laundry carefully, wipe down surfaces with a bleach-based cleaner, wash fruits and vegetables, thoroughly cook foods and avoid preparing meals if infected.