Physicians in the United Kingdom’s National Health Service say they have seen an increase in cases of Kawasaki disease in pediatric patients with COVID-19.

Primarily affecting children, Kawasaki disease is an inflammatory condition that affects the walls of coronary arteries that supply blood to heart muscle, according to Mayo Clinic.

National Health Service England sent an alert to doctors and on Sunday the Pediatric Intensive Care Society tweeted it out to members. It warned about a small increase in cases of critically ill children with “common overlapping features of toxic shock syndrome and atypical Kawasaki disease with blood parameters” with some children testing positive for COVID-19. There have also been some reports in Italy and Spain, doctors said.

A team at Stanford Children’s Hospital said they had also seen a case. They described the case of a 6-month-old girl admitted to the hospital with Kawasaki disease and later also diagnosed with coronavirus.