Norovirus Outbreaks Increased in Nursing Homes in 2006
In the recent issue of the Morbidity and Mortality Weekly Report (MMWR), the CDC reports its analysis of the incidences of outbreaks of acute gastroenteritis (AGE), including norovirus outbreaks. The CDC analysis suggests that a national increase has occurred in the frequency of AGE outbreaks caused by norovirus (including fatal cases in long-term–care facilities). One reason for this increase is that two new norovirus strains emerged nationwide in 2006. People were not immune to these strains.
The CDC looked at the incidences of AGE in certain states, including North Carolina, Wisconsin, and New York, and solicited information from the health departments of all 50 states and the District of Columbia. The following are excerpts from the MMWR article:
North Carolina
During January–December 2006, the North Carolina Division of Public Health received 17 reports of outbreaks clinically and epidemiologically consistent with norovirus infection among residents of long-term–care facilities, compared with six in 2005 and three in 2004. Norovirus was confirmed by reverse transcription–polymerase chain reaction (RT-PCR) in all 12 outbreaks for which stool specimens were available. A total of 573 residents and 288 staff members were affected in the 17 outbreaks, and 36 patients required hospitalization. One patient aged 90 years died in association with an AGE outbreak in a long-term–care facility after experiencing loose stools, fever, and dehydration for 3 days; gastrointestinal illness was recorded as the primary cause of death.
Wisconsin
During 2006, the Wisconsin Division of Public Health received reports of 106 AGE outbreaks, compared with 23 AGE outbreaks in 2005. Eighty-seven (82%) of the 2006 outbreaks were PCR-confirmed norovirus outbreaks; 45 (78%) of 58 norovirus-confirmed, nonfoodborne outbreaks were in longterm–care facilities, compared with three (20%) of the 15 norovirus-confirmed, nonfoodborne outbreaks in 2005. The 45 outbreaks in long-term–care facilities reported in Wisconsin in 2006 included 2,071 clinical cases; 44 patients were hospitalized, and two died.
New York
During October 1, 2006–January 31, 2007, a total of 333 AGE outbreaks were reported in New York, more than four times the number reported during the same period in 2005–2006 (76 outbreaks). Of these 333 outbreaks, 272 (82%) occurred in long-term–care facilities and 26 (8%) in hospitals. Of 216 health-care facility outbreaks with available data, a total of 7,907 patients and 4,317 staff members were affected. Of these, 207 (2.6%) patients and 20 (0.5%) staff members were hospitalized, and 16 deaths among patients with AGE were reported; however the cause of death was not reported. In October 2005, electronic reporting of outbreaks in health-care facilities began in New York, which might have increased the completeness of reporting from these facilities. However, the number of outbreaks reported by traditional means (i.e., fax machine or telephone) increased 298%, from 42 during the 2005–2006 period to 167 during the 2006–2007 period, suggesting a real increase in incidence.
United States
CDC reviewed data from 24 states that reported at least five outbreaks in both 2005 and 2006 These 24 states reported a total of 1,316 AGE outbreaks withonset during October–December 2006; a median of 50% occurred in long-term–care facilities, and a median of 26% had laboratory confirmation of norovirus by RT-PCR. Of these 24 states, 22 (92%) reported an increase in the number of outbreaks compared with the same period in 2005 (range of increase: 18%–800%). State officials reported that the majority of the outbreaks with no laboratory confirmation of norovirus had epidemiologic and clinical evidence suggestive of norovirus infection.
To read the full text of the MMWR article on Norvirus, please click here. The article appears on page 842.