Norovirus is the name for a group of viruses that can cause serious gastroenteritis, a stomach illness. The virus is primarily spread through contact with contaminated fecal matter or vomit (like when caring for a sick person). However, there are several other ways people can be infected. Airborne virus particles land on surfaces and infect others who touch the contaminated surfaces. Doorknobs, countertops and even food can be contaminated by a sick person who doesn't follow good hand washing hygiene. Researchers say cruise ship passengers who drink contaminated water in a destination country can bring the virus back on board and spread the infection to a large number of passengers.
Symptoms of Norovirus infection typically appear suddenly, within one to two days of transmission. The most common signs are stomach pain or cramps, diarrhea nausea and vomiting. Other signs can include low-grade fever, body aches, chills, weakness and fatigue. In most cases, the symptoms ease within one to three days. Young children, the elderly and those with chronic health problems or weak immune systems may have prolonged and/or more serious symptoms, leading to dehydration, weight loss, kidney failure, and, in some cases, death. About one-third of those who are infected don't develop any signs of illness.
The first cases of Norovirus were reported in Norwalk, OH in 1968. Today, it's the most common cause of gastroenteritis epidemics in the world, accounting for half of all outbreaks of stomach viruses. According to the CDC, about 21 to 23 million cases occur in the U.S. each year. Groups at highest risk for Norovirus infections are restaurant diners, children, the elderly, those with weakened immune systems, cruise ship passengers, members of the military, and residents of hospitals, nursing homes and other long term care facilities.
A Vaccine for Norovirus?
Norovirus infections are very contagious and extremely difficult to control, especially in closed environments (like a cruise ship). Experts say only 18 virus particles are needed to cause an infection. The virus can persist on surfaces and is often resistant to standard cleaning agents. People who have been sick can also continue to shed virus particles for up to 8 weeks after symptoms have gone away.
Researchers at the University of Rochester Medical Center in Rochester, NY are now testing a potential vaccine for Norovirus. The vaccine aims to provide protection from the two most common strains of the virus. Infectious Disease Specialist, John Treanor, M.D., estimates that would cover about 80 percent of cases occurring in the U.S.
The first phase of the study is designed to look at various doses of the vaccine. The investigators will measure immune response for each dose and monitor participants for side effects. Since the vaccine is in very early stages, researchers don't know when it will be given or how often it will be needed. Treanor says it's possible patients may need booster doses to keep their immunity. Another potential use may be to give the vaccine right before any high risk exposure (like a cruise).
In the meantime, the best way to reduce risk for Norovirus infection is to thoroughly wash your hands with running water and soap. This is especially important for anyone who has developed signs of a stomach illness. In closed environments (like a hospital, nursing home or cruise ship), health care providers may opt to keep people who are ill in isolation to reduce the risk for spreading the illness to others. Surface decontamination (especially in bathrooms and high traffic areas) is also very important to eliminate all possible sources of transmission.
Research compiled and edited by Barbara J. Fister
Centers for Disease Control and Prevention, http://www.cdc.gov/ncidod/dvrd/revb/gastro/norovirus.htm
National Institute of Allergy and Infectious Diseases,