Parents have been issued with a rare health alert over rapidly increasing numbers of Strep A infections now believed to have led to the deaths of at least six children and left hundreds of youngsters unwell.

Health officials are urging families to trust their own judgement and seek medical help if their child is seriously sick as medics try to understand what might be causing such high rates of infection this winter.

But with so many coughs and colds circulating what health issues can a Strep A infection cause, how common is it to be infected and what are the signs and symptoms parents should be looking for?

What is Strep A?

Strep A - or Group A streptococcus (GAS) - is a bacteria found in the throat and on the skin. In many people it won't cause any symptoms at all while others may be unwell - but crucially those carrying the infection can pass it on to others in the same way that those who are sick can.

Strep A can be the cause of a range of different illnesses that affect the nose, throat and lungs. These include tonsillitis, scarlet fever and impetigo - a relatively common but not often serious skin infection which causes sores and blisters.

But Strep A infections become far more serious when the bacteria enters parts of the body where it wouldn't normally be found such as the blood stream or lungs. It is here where it causes a more serious illness called invasive Group A Strep (iGAS).

While health officials say this type of very serious illness is rare, there has been an increase in invasive Group A strep cases this year, particularly in children under 10, which has prompted health officials to ask parents and medics to be on their guard.

How many cases have there been?

There are currently around 2.3 cases of iGAS, or invasive Group A strep, per 100,000 children aged one to four compared to an average of 0.5 cases per 100,000 in the pre-pandemic seasons between 2017 and 2019.

In children aged five to nine there are now 1.1 cases per 100,000 children compared to a pre-pandemic average of 0.3 cases - so while the infection is rare - numbers are increasing.

On Friday, the UK Health Security Agency announced there have also been five recorded deaths confirmed to have been within seven days of an iGAS diagnosis in children under 10 in England, while during the last high season for Group A Strep infection (2017 to 2018) there were 4 deaths in children under 10 for the equivalent period. A child under 10 has also died in Wales.

Recorded incidents of scarlet fever in England, one of the illnesses known to be caused by circulating Strep A bacteria, also reached 851 during one particular week in mid-November compared to an average of just 186 cases for the same week in previous years.

In the South East there have been 637 cases of scarlet fever (a rate of 7.1 per 100,000 children) and 80 cases of iGAS (a rate of 0.9 per 100,000) between September 12 and November 20 this year.

Investigations are also under way, say government health officials, following reports of an increase in lower respiratory tract Group A infections in children over the past few weeks, which are also causing more severe illness than is normally seen in such numbers.

Is this a new more dangerous strain?

There is no new evidence, says the UKHSA, that a new or more dangerous strain of Strep A is circulating. The increase is more likely to be related to high amounts of circulating bacteria and social mixing, which has been historically lower during the last two years because of pandemic restrictions.

In an interview on Radio 4 on Monday morning UKHSA chief medical advisor Dr Susan Hopkins said the theory that a higher than normal spread of Strep A infections is connected to the Covid-19 pandemic was being explored.

She explained: "Firstly, I think that we’re seeing a lot of viral infections circulate at the moment and these bacterial infections can come as an addition on top. Secondly, we’re back to normal social mixing and the patterns of diseases that we’re seeing in the last number of months are out of sync with the normal seasons as people mix back to normal and move around and pass infections on.

"We also need to recognise that the measures that we’ve taken for the last couple of years to reduce Covid circulating will also reduce other infections circulating. And so that means that, as things get back to normal, these traditional infections that we’ve seen for many years are circulating at great levels."

Signs and symptoms of Strep A infections?

There are lots of viruses causing sore throats, colds and coughs currently circulating, admits the UKHSA, which should resolve without any medical treatment.

There has also been a rise in the numbers of children needing treatment for complications connected to the flu virus - where cases at the end of November leapt by 70% over the course of just a week with more than 200 children being admitted to hospital.

In an interview with the Sunday Telegraph, Kent GP Stephanie de Giorgio who works in urgent care said medics are seeing a lot of children with respiratory infections, such as coughs and colds, while managing the pressure of not missing a more serious infection.

She said: "I won’t lie, I am terrified of missing this.

"GPs, and those working in urgent and emergency care, are seeing huge numbers of children with viral upper respiratory infections. No one wants to miss a serious diagnosis."

Symptoms connected to a Strep A infection can include pain when swallowing, a fever, swollen tonsils that have visible white patches on them, swollen neck glands, a high temperature or skin rash.

Children with scarlet fever are likely to have a rough-feeling skin rash that feels like sandpaper to touch and can develop what is described as a 'strawberry tongue' - where their tongue turns a very bright red colour and has white flecks of coating on it that resembles the outside of a strawberry.

Dr Susan Hopkins, during her Radio 4 interview, added that parents should be particularly vigilant when it comes to a sore throat and fever that don't go away with normal painkilling treatments alongside children who appear unusually drowsy and aren't using the toilet as much as they normally would or producing as many wet nappies as normal.

In its own warning to parents the UKHSA said families should trust their own judgement and contact their GP or NHS 111 if they feel that their child seems seriously unwell.

Signs including worsening symptoms, eating or feeding less than normal, having a dry nappy for 12 hours or more, extreme tiredness or irritability, a temperature of 38C if under three months or 39C if older than three months and a feeling that a child's skin is hotter or sweatier than normal are all also signs, it says, that should not be ignored.

Dr Colin Brown, Deputy Director, UKHSA, added: "We are seeing a higher number of cases of Group A strep this year than usual. The bacteria usually causes a mild infection producing sore throats or scarlet fever that can be easily treated with antibiotics. In very rare circumstances, this bacteria can get into the bloodstream and cause serious illness – called invasive Group A strep (iGAS).

"This is still uncommon; however, it is important that parents are on the lookout for symptoms and see a doctor as quickly as possible so that their child can be treated and we can stop the infection becoming serious.

"Make sure you talk to a health professional if your child is showing signs of deteriorating after a bout of scarlet fever, a sore throat, or a respiratory infection."

Any child having difficulty breathing - including making grunting noises or sucking their tummy under their ribs, or who has skin, a tongue or lips which appear blue or who is floppy and will either not wake up or stay awake should be taken straight to A&E or be called an ambulance using 999.