New norovirus strain reaches U.S.
A new strain of norovirus, the cause of a dreaded wintertime intestinal illness, is circulating in the United States, federal health officials said on Thursday.
The strain, designated “GII.4 Sydney,” appeared in Australia in 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.
“We don't yet know whether there is an increased number of cases this year,” said Jan Vinje, the CDC epidemiologist who runs the network. “Normally the season peaks in January, so it's a little bit too early to tell.”
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 notoriously 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 werecaused by contaminated water. The mode of transmission was unknown in the rest.
About two-thirds of this season's outbreaks occurred in long-term care institutions and 13 percent involved restaurants, according to the CDC's Morbidity and Mortality Weekly Report.
As a norovirus strain spreads, people become at least partly immune to it. The “herd immunity” that develops favors the emergence of new, slightly different strains against which people have less protection.
“It's a little like flu,” Vinje said. “The virus is mutating to a ‘fitter' strain and is attacking a non-immune population.”
There are five main types of norovirus (denoted GI through GV), with most outbreak viruses falling into one subgroup, GII.4. Historically, GII.4 strains are more severe than others. Whether that will be true this year is not yet known.
Show commenting policy
TribLive commenting policy
You are solely responsible for your comments and by using TribLive.com you agree to our Terms of Service.
We moderate comments. Our goal is to provide substantive commentary for a general readership. By screening submissions, we provide a space where readers can share intelligent and informed commentary that enhances the quality of our news and information.
While most comments will be posted if they are on-topic and not abusive, moderating decisions are subjective. We will make them as carefully and consistently as we can. Because of the volume of reader comments, we cannot review individual moderation decisions with readers.
We value thoughtful comments representing a range of views that make their point quickly and politely. We make an effort to protect discussions from repeated comments either by the same reader or different readers.
We follow the same standards for taste as the daily newspaper. A few things we won't tolerate: personal attacks, obscenity, vulgarity, profanity (including expletives and letters followed by dashes), commercial promotion, impersonations, incoherence, proselytizing and SHOUTING. Don't include URLs to Web sites.
We do not edit comments. They are either approved or deleted. We reserve the right to edit a comment that is quoted or excerpted in an article. In this case, we may fix spelling and punctuation.
We welcome strong opinions and criticism of our work, but we don't want comments to become bogged down with discussions of our policies and we will moderate accordingly.
We appreciate it when readers and people quoted in articles or blog posts point out errors of fact or emphasis and will investigate all assertions. But these suggestions should be sent via e-mail. To avoid distracting other readers, we won't publish comments that suggest a correction. Instead, corrections will be made in a blog post or in an article.
- D.C. charges woman over armed protest
- NSA: China thefts could lead to attack
- Obama defers deportations for 4 million illegals
- Former nuke commander linked to fake poker chips
- New nuke carrier will arrive late, incomplete
- Ferguson, Mo., grand jury to meet Monday, decide on possible indictment of police officer