Health officials are conducting an investigation after a nationwide surge in hepatitis infections in children.

Since the start of the year there have been 111 cases where youngsters have required medical treatment for inflammation of the liver, with the majority occurring in children under five.

Ten young patients have needed a liver transplant.

The current theory is that the rise in infections have been fuelled by a common virus called adenovirus - and the lack of exposure to it during the pandemic.

Here is what you need to know.

What is hepatitis?

“Hepatitis is inflammation of the liver. There are various causes of hepatitis, including viral infections and alcohol consumption,” said Dr Stephanie Ooi, a GP at the MyHealthcare Clinic in London.

“Some cases of hepatitis will resolve with no ongoing issues; however, there are certain cases that can be longer lasting, and cause more serious damage to the liver, and affect liver function.”

According to the NHS, hepatitis E – caused by the hepatitis E virus – is the most common cause of short-term (acute) hepatitis in the UK.

What are the symptoms?

According to the NHS, short-term (acute) hepatitis often has no noticeable symptoms, so you may not realise you have it.

If you do experience symptoms, Dr Ooi said: “You may notice a high temperature, jaundice (yellowing of the eyes and skin), fever, generally feeling unwell, dark-coloured urine and pale-coloured stool. In addition you may have tummy pain, have a reduced appetite and itchy skin.”

The NHS lists muscle and joint pain and feeling unusually tired all the time as further symptoms.

What should parents and carers do?

“The number of cases of hepatitis in children is increasing, which is understandably causing some concern amongst parents,” said Dr Ooi. “The best thing to do is to see your GP if you notice any of the above symptoms, and are worried about hepatitis.

“Some of the symptoms can present in other conditions, so it does not necessarily mean your child has hepatitis – but jaundice in particular needs to be urgently highlighted to a doctor.”

Dr Meera Chand, director of clinical and emerging infections at the UKHSA, said: “Normal hygiene measures such as thorough handwashing (including supervising children) and good thorough respiratory hygiene, help to reduce the spread of many common infections, including adenovirus.

“Children experiencing symptoms of a gastrointestinal infection, including vomiting and diarrhoea, should stay at home and not return to school or nursery until 48 hours after the symptoms have stopped.”

What are the treatment options?

Dr Ooi said: “The treatment will depend on what is causing the hepatitis, so this will vary. Your child will be assessed and monitored and have any further tests that need to be done.

“Treatment will also be based on symptoms, i.e. giving adequate pain relief if they are in pain or feeling uncomfortable.”

In very serious cases, sufferers might need a liver transplant.

What we know so far

The leading line of inquiry is that the cases are being fuelled by a common virus called the adenovirus.

This virus usually causes mild illnesses including stomach upsets and colds.

But one theory is that the virus is leading to more severe illness among some children due to “susceptibility, for example due to lack of prior exposure during the pandemic”, according to a technical briefing from the UK Health Security Agency (UKHSA).

Of 53 cases tested, 40 (75pc) showed signs of adenovirus infection.

Routine NHS and laboratory data show that common viruses circulating in children are currently higher than in previous years and there is a marked increase of adenovirus, particular in the one to four age group, the UKHSA said.

Other avenues being explored include whether a prior Covid infection followed by an adenovirus infection could be leading to more severe cases or co-infection with the two viruses.

Experts are also examining other possible causes including a new variant of adenovirus; potential exposure to drugs, toxins or environmental factors; a new type of infection; or a new variant of the virus which causes Covid.

Covid-19 vaccination is not a contributing factor as none of the cases investigated so far have been vaccinated.

Of the confirmed cases, 81 live in England, 14 are in Scotland, 11 are in Wales and five are in Northern Ireland.

The cases are predominantly in children under five who showed initial symptoms of diarrhoea and nausea followed by jaundice.