Nearly 600 children were admitted to U.S. hospitals with a rare inflammatory syndrome associated with the novel coronavirus over four months during the peak of the pandemic, the Centers for Disease Control and Prevention (CDC) said in a report on Friday.

Multisystem inflammatory syndrome (MIS-C) is a rare but severe condition that shares symptoms with toxic shock and Kawasaki disease, including fever, rashes, swollen glands and, in severe cases, heart inflammation.

It has been reported in children and adolescent patients about two to four weeks after the onset of COVID-19.

With rising COVID-19 cases, there could be an increased occurrence of MIS-C, but this might not be apparent immediately because of the delay in development of symptoms, said the report’s authors, including those from the CDC’s COVID-19 response team.

In May, the CDC published a health advisory with details of how MIS-C manifests in patients, and asked clinicians to report suspected U.S. cases to local and state health departments.

As of July 29, state health departments across the country reported a total of 570 MIS-C patients diagnosed with the illness from March 2 to July 18.

Among the MIS-C cases, all patients tested positive for COVID-19 and 10 died, the CDC said in the report.

The data is consistent with two U.S. studies published in June and several reports of the syndrome among COVID-19 patients in France, Italy, Spain and Britain.

The report, the CDC said, highlights the need for greater awareness among healthcare providers, as distinguishing patients with MIS-C from those with acute COVID-19 and other hyperinflammatory conditions is critical for early recognition, early diagnosis, and prompt treatment.