The coming norovirus season could put intense pressure on the NHS, with cases already 55% higher than usual, Public Health England (PHE) has warned.
"It is possible that unusual or out of season increases in norovirus activity could be seen in the coming months," a PHE report said.
Norovirus, which causes vomiting and diarrhoea, tends to peak in winter.
PHE said: "The total number of reports was 55% higher than the average of the same period in the previous five seasons pre-COVID-19."
There are concerns norovirus could cause havoc in care homes as there has been a "notable" increase in the number of outbreaks in care settings.
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Despite norovirus usually spreading quickly through younger generations, the report said PHE had seen a decline in educational settings.
This may change due to the report covering a period where most schools had not yet fully returned from their summer break.
The report covered the period from the week starting on August 29.
Several notable outbreaks of norovirus have also been reported in nurseries and other child care settings.
Norovirus cases had been considerably lower during lockdown, but now they are effectively over across the UK it could lead to an even harsher resurgence.
A spike in norovirus, particularly among the elderly, could put increased pressure on the NHS amid fears there will already be difficult times ahead as cases of COVID-19 increase.
In July, England's chief medical officer, Professor Chris Whitty, said winter "could be tricky" due to the double whammy of higher numbers of seasonal viruses like norovirus as well as COVID-19.
Senior NHS chiefs have also warned the health service is heading for one of the most difficult winters in its history.
Saffron Cordery, deputy chief executive of NHS Providers, told iNews earlier this week: "The NHS is likely to face one of the most challenging winters on record as it tackles the backlog of care, the continuing presence of COVID-19, potentially high levels of flu and RSV [respiratory syncytial virus] and general winter pressures.
“This is all combined with a stretched NHS workforce that is currently grappling with serious staffing pressures and rapidly growing urgent care demand across all parts of the health and care system.”
There have been rumours recently about the government preparing to implement a firebreak lockdown around the October half term due to dears of pressure on the NHS, although ministers have denied this.
The prime minister’s official spokesman said the vaccination programme provides “significant defences” which the country did not have on previous occasions when restrictions were put in place.
Downing Street denied there is a plan to put in place a firebreak this autumn if there is a new surge in COVID-19 cases, but the government said there are “contingency plans” for a “range of scenarios”.