Cases of norovirus in England have increased significantly and were more than double the five-season average before the onset of COVID-19, latest figures showed.
Reports of suspected and confirmed norovirus outbreaks in hospitals also increased compared with previous weeks, but remained below the five-season average, the UK Health Security Agency (UKHSA) reported.
Reporting increased across all age groups, but Dr Lesley Larkin, surveillance lead at the Gastrointestinal Infections and Food Safety Division at UKHSA, said: "Most reported cases are in the over 65s and we're also seeing an increase in reported outbreaks, particularly in care home settings." Outbreaks reported in care homes increased from 47 in the week commencing 6 February to 54 in the week commencing 13 February 2023, which the Agency said was the highest number of outbreaks reported in a week so far this season.
Dr Larkin said that overall, "norovirus levels are currently the highest we have seen at this time of year in over a decade".
The latest report provided a summary of norovirus and rotavirus activity, including enteric virus (EV) outbreaks, and covered a 2-week period between 6 and 19 February.
The cumulative number of positive norovirus laboratory reports in England this season was 24% higher compared with the five-season average for the same period between 2014-15 and 2018-19. So far this season there have been 4551 laboratory reports of norovirus, compared with the average of 3661 cases across the pre-pandemic seasons.
Cases of norovirus went through a sustained period of unusually low activity during the pandemic when social distancing measures were in place but began to rise when restrictions were lifted.
Scientists at the Agency said that 80% of samples tested were norovirus genogroup 2 (GII), of which the most frequently identified strain was genotype GII.4, which was seen in 45% of the samples.
Outbreaks in Care Homes
While reported EV outbreaks showed an increasing trend in recent weeks, the number of reported outbreaks was 31% lower than the pre-pandemic five-season average. Before the onset of COVID-19, most EV outbreaks were confined to hospitals and care homes, but shifted during the pandemic to schools and other educational settings. During the current season, the majority of EV outbreaks have occurred in care homes.
The cumulative number of positive rotavirus laboratory reports in England up to 19 February stood at 1071, which was 14% below the average 1245 reports seen in the 5 years preceding COVID-19.
Overall rotavirus activity for the 2-week period of weeks 6 and 7 2023 (93 laboratory reports) was 35% lower than the 5-season average (102 laboratory reports) for the same period.
The UKHSA renewed its call to the public to take precautions against infection, including by regular hand washing. "Alcohol gels do not kill off norovirus, so washing with soap and warm water is best," said Dr Larkin. The Agency also advised anyone with norovirus symptoms to avoid visiting hospitals and care homes until 48 hours after symptoms have passed.