A new strain of norovirus, the cause of a dreaded wintertime intestinal illness, is circulating in the United States, federal health officials have announced.
The strain, designated “GII.4 Sydney,” appeared in Australia last March. It is also spreading in Britain, where it caused an early start of the norovirus season. In the United States it has caused half of the 266 norovirus outbreaks reported since September to a surveillance network run by the Centers for Disease Control and Prevention.
Norovirus causes vomiting and diarrhea. It is responsible for 21 million cases of illness a year in the United States, and about 800 deaths, mostly among the elderly. There is no specific treatment for it and no vaccine, although one is under development. Hand-washing, wiping down contaminated surfaces and isolating people who are ill are the typical strategies for combating norovirus.
Outbreaks are associated with nursing homes and cruise ships, but norovirus also spreads easily through the general population. In the outbreaks since September, 51 percent involved person-to-person transmission; 20 percent were foodborne; and 1 percent were caused by contaminated water.