Health authorities in the United Kingdom (TADAWUL:4280) (UK) have issued a warning this week about a potential second wave of norovirus, citing fresh data indicating a shift in circulating strains.According to the latest data from the UK Health Security Agency (UKHSA), norovirus cases are on the rise across the country, reaching their highest level since reporting began in 2014.

The UKHSA reports that cases of the virus increased by over 30% between February 3 and 16 compared to the previous fortnight, and were more than double the five-season average.

According to the health department, the impact is most severe in hospitals and care homes, with the majority of cases occurring among those aged 65 and more.

Cases often begin to fall around this time of year as the weather warms up, but the UKHSA says it is too early to say if norovirus has peaked this season.

The most recent data also reveal a shift in circulating strains, with an increase in cases this season associated with the novel GII.17 genotype. Meanwhile, Xinhua stated that the GII.4 genotype is rising.

Vomiting, diarrhea, and stomach cramping are among the most common symptoms of norovirus infection. The virus can occasionally cause low-grade fever or chills, headaches, and muscle aches. These symptoms usually appear one to two days following infection.

In December, there were an exceptionally large number of norovirus outbreaks reported in the United States.

According to the Centers for Disease Control and Prevention (CDC), outbreaks can occur at any time of year, but are most likely between November and April.

The extremely contagious virus, which infects an estimated 19 to 21 million people annually, can cause sudden and unpleasant gastrointestinal symptoms, according to the CDC.