A serious coronavirus-related syndrome may be emerging in the UK, according to an “urgent alert” issued to doctors, following a rise in cases in the last two to three weeks, HSJ has learned.

An alert to GPs and seen by HSJ says that in the “last three weeks, there has been an apparent rise in the number of children of all ages presenting with a multisystem inflammatory state requiring intensive care across London and also in other regions of the UK”.

It adds: “There is a growing concern that a [covid-19] related inflammatory syndrome is emerging in children in the UK, or that there may be another, as yet unidentified, infectious pathogen associated with these cases.”

Health secretary Matt Hancock later told the government’s daily press briefing he is “very worried” about signs of a new coronavirus-linked syndrome in children and these are being investigated “as a matter of urgency”.

Little is known so far about the issue, nor how widespread it has been, but the absolute number of children affected is thought to be very small, according to paediatrics sources. The syndrome has the characteristics of serious covid-19, but there have otherwise been relatively few cases of serious effects or deaths from coronavirus in children. Some of the children have tested positive for covid-19, and some appear to have had the virus in the past, but some have not.

The fact that very few children have become seriously ill with the virus or died, compared to adults, remains the case.

The alert was issued to GPs in North London by their clinical commissioning group. It has been sent to doctors more widely and is confirmed in a separate “urgent alert” issued last night by the Paediatric Intensive Care Society.

The alert to GPs, marked “significant alert” states: “Please refer children presenting with these symptoms as a matter of urgency.”

Both messages said: “The cases have in common overlapping features of toxic shock syndrome and atypical Kawasaki Disease with blood parameters consistent with severe COVID-19 in children.

“Abdominal pain and gastrointestinal symptoms have been a common feature as has cardiac inflammation. This has been observed in children with confirmed PCR positive SARS-CoV-2 infection as well as children who are PCR negative. Serological evidence of possible preceding SARS-CoV-2 infection has also been observed.”

PICS advised “early discussion” of possible cases “with regional paediatric infectious disease and critical care teams”.

Simon Kenny, NHS England’s national clinical director for children and young people, said: “Thankfully Kawasaki-like diseases are very rare, as currently are serious complications in children related to Covid-19, but it is important that clinicians are made aware of any potential emerging links so that they are able to give children and young people the right care fast.

“The advice to parents remains the same: if you are worried about your child for whatever reason, contact NHS 111 or your family doctor for urgent advice, or 999 in an emergency, and if a professional tells you to go to hospital, please go to hospital.”

Updated 9.30am: Added bullet points and clarified text and at 1pm to add a comment from the national clinical director. Updated at 10:50 on 28 April to add information from government daily press briefing