Scientists reveal the exact reason why a norovirus doesn't have a vaccine yet

Norovirus swept across the nation this winter and everybody seems to know someone who was struck down by the seasonal illness. The anecdotal evidence is backed up by the NHS data, which shows unprecedented numbers of patients presenting with the winter vomiting bug.

There was an average of 1,160 daily hospital patients suffering from norovirus throughout the second week of February. This represents a 22% spike from the previous week and more than a twofold increase from the same period last year, which saw 509 cases.

In addition to norovirus, hospitals are also seeing a surge in respiratory syncytial virus (RSV) infections, with an 83% rise from the prior week and a staggering 144% jump compared to last year's figures.

Norovirus symptoms are impossible to ignore and make for a few extremely unpleasant days, as anyone unlucky enough to have caught it will testify. The diarrhea, vomiting and nausea impacts the youngest, the oldest and the immunocompromised the most.

Despite the virus infecting 685 million people across the globe every year and killing 200,000, there is still no vaccine for the disease. The World Health Organisation (WHO) has prioritised developing a norovirus vaccine due to the huge costs of the illness, $4billion in healthcare and $60billion in terms of cost to society.

There are a few candidate jabs making their way through clinical trials but it is a tricky virus with some information gaps. There are ten different groups of norovirus, which are subdivided into 49 different types.

Five or half of the groups are known to infect people. The range of different vomiting bugs is part of the challenge of developing an effective vaccine.

Virologist Christiane Wobus said: "The biggest problem we have to deal with is the genetic diversity — there’s lots of different flavors” of norovirus.

This means boffins do not know how many types of norovirus a vaccine needs to tackle in order to provide enough protection. With strong progress being made in clinical trials, a jab is likely to arrive but the timing is still unclear.