Over three quarters of flu infections contracted last year did not have any symptoms, researchers found.
Most of the infections (77%) didn't have any symptoms despite one in five people contracting either seasonal flu and the 2009 H1N1 influenza pandemic.
According to The Lancet Respiratory Medicine Journal:
- Researchers found that on average, 18% of people who had not received a flu jab were infected with flu each season.
- And only 17% of those infected felt ill enough to visit their GP.
- Over the winter flu season, 4.7% of people were believed to have flu compared to 6% the previous year.
- Some 5% of children were reported to have flu, compared to almost 8% the previous year.
More research will need to be done into the effects of vigorous exercise in warding off the flu, but fresh data shows it can help reduce the chance of catching it, experts have said.
Dr Alma Adler, research fellow at the London School of Hygiene and Tropical Medicine, explained:
Two-and-a-half hours of vigorous exercise every week cut the chance of catching the flu by approximately 10%, research suggests.
Physical activity which leads to sweating or hard breathing reduces flu or flu-like illness, experts at the London School of Hygiene and Tropical Medicine found.
Walking, light jogging and other gentle sports which did not raise heart rate, were found to have little effect.
The Flusurvey also found overall flu levels across the UK appear to be down on last year, with the influenza season apparently curbed by a lack of illness among children and young people.
Part of a pilot programme to vaccinate schoolchildren in Scotland against flu has been delayed over concerns from the Muslim community that it contains traces of pork, the BBC reports.
Pupils at 100,000 primary schools are being offered the Fluenz vaccine as a nasal spray, but parents have raised concerns that the spray contains gelatine which is derived from pork.
NHS Greater Glasgow and Clyde, whose area contains most of Scotland's Muslims, said it had put back the rollout of the vaccinations "following concerns raised by a small number of parents".
Scottish health minister Michael Matheson said an investigation including Muslim scholars had concluded that the sprays could be used, but added that anyone with concerns could opt for a standard jab.
The Government's plans to encourage NHS trusts to ensure three quarters of their workers are vaccinated from the flu "is a very welcome initiative", a lung and heart expert has told Daybreak.
Professor Peter Openshaw, director of the Centre for Respiratory Infection, welcomed plans to encourage NHS trusts to make sure their workers are properly immunised by allowing them access to some of the £250 million funding.
NHS trusts that fail to prove at least 75% of their workers have had the jab will be blackballed from emergency funding.
Three quarters of the workforce in every NHS trust will have to be vaccinated against flu this year or miss out on the £250 million pledged by the Government to fight the disease.
- This extends to the wider workforce outside of clinicians - managers, porters and other hospital workers will have to be immunised.
- New data shows just 8% of staff at Britain's worst performing hospitals had been given the flu vaccine, compared with 80% at the best.
- The average was 45% - a level described by Dame Sally Davies, the UK's chief medical officer, as really not good enough.
According to health secretary Jeremy Hunt, the £250 million the Government has pledged to tackle the perennial flu problem will be used to protect some of the UK's youngest children against the disease.
- Two and three year olds in England will be offered flu vaccinations as part of the new initiative to tackle winter health problems.
- GPs will administer a single dose nasal spray to toddlers alongside the annual campaign to vaccinate Britain's elderly and vulnerable.
- The nasal spray flu vaccine is also for children aged two to 18 who are 'at risk' from flu, such as children with long-term health conditions.
The Government is injecting millions into the flu vaccination programme on the condition NHS trusts prove at least 75% of their staff have been immunised against the disease.
Two pots of £250 million have been set aside to fund the programme this year and in 2014.
However, health secretary Jeremy Hunt said NHS trusts would only have access to the funds when they could prove 75% of their workforce had already been immunised against the flu.
Scientists have found a "blueprint" for a universal flu vaccine, according to the leader of a research project into influenza, said Professor Lalvan:
British scientists are one step closer to developing a "holy grail" universal flu vaccine that would tackle all strains of the illness.
A successful jab would stimulate the body to create more immune cells capable of attacking the virus and could be effective at preventing new strains that cross into humans from birds and pigs, according to scientists.
Results from the 2009 swine flu pandemic showed patients with more virus-killing immune cells in their blood at the start of the illness, would avoid sever illness, researchers at Imperial College London (ICL) found.
Professor Ajit Lalvani from the National Heart and Lung Institute at ICL, who led the study, said: "New strains of flu are continuously emerging, some of which are deadly, and so the holy grail is to create a universal vaccine that would be effective against all strains of flu."
Influenza kills between 250,000 and 500,000 globally per year, according to the World Health Organisation.