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This award-winning blog supplements the articles in Hospital Infection Control & Prevention.

Mysterious Post-Infection COVID-19 Syndrome now in Adults

By Gary Evans, Medical Writer

First seen in children, a troubling and poorly understood multisystem inflammatory syndrome (MIS) linked to COVID-19 is now emerging in adults. The syndrome, called MIS-C in children and MIS-A in adults, can appear in the absence of respiratory symptoms and cause serious and fatal outcomes.

Findings indicate that adult patients of all ages with current or previous SARS-CoV-2 infection can develop a hyperinflammatory syndrome resembling MIS-C, the CDC reported.

“Although hyperinflammation and extrapulmonary organ dysfunction have been described in hospitalized adults with severe COVID-19, these conditions are generally accompanied by respiratory failure,” the CDC states. “In contrast, the patients described here had minimal respiratory symptoms, hypoxemia, or radiographic abnormalities in accordance with the working case definition, which was meant to distinguish MIS-A from severe COVID-19; only eight of 16 patients had any documented respiratory symptoms before onset of MIS-A.”

The pathophysiology of MIS in both children and adults is currently unknown, the CDC noted.

“Eight of 27 (30%) adults described in this report and 45% of 440 children with MIS-C reported to CDC through July 29, 2020, had negative PCR and positive SARS-CoV-2 antibody test results, suggesting MIS-A and MIS-C might represent post-infectious processes,” the CDC said. “All but one of the patients with MIS-A described in this report belonged to racial or ethnic minority groups.”

Hospital Employee Health submitted questions to CDC investigators and received the following answers, which have been edited for clarity.

HEH: Can you describe what differences — if any — you are seeing in this syndrome in adults compared to children?

CDC: Researchers have described multisystem inflammatory syndrome in children since April 2020. This review describes nine adult patients reported to CDC, seven published case reports, and summarizes the findings in 11 adult patients described in three published case series. Children are more likely to have asymptomatic or mildly symptomatic COVID-19 than adults. In this case report, the patients had less dermatologic and gastrointestinal involvement than the numbers reported in children.

HEH: Can you provide more detail on the adult patients?

CDC: These 27 patients with MIS-A had signs and symptoms in various parts of the body (such as the heart, digestive tract, nervous system, or skin) and didn’t have severe respiratory illness. Although some patients had positive viral tests, antibody testing was required to identify infection with the virus that causes COVID-19 in approximately one-third of the 27 cases. A positive antibody test indicates previous infection. In the working case definition used in this description, the lack of respiratory symptoms at presentation represents the main distinction between patients with severe COVID-19 and MIS-A. Patients may present with multiorgan dysfunction without history of symptomatic SARS-CoV-2 infection or acute COVID-19, thus requiring an antibody test to confirm the diagnosis.

HEH: What were the morbidity and mortality outcomes for these patients?

CDC: The 16 patients reported to CDC and in published case reports ranged in age from 21 to 50 years and included seven men and nine women. Nine patients had no reported underlying medical conditions; six had obesity, one had poorly controlled type 2 diabetes, two had hypertension, and one had sleep apnea. Six patients were initially evaluated for possible heart trouble symptoms such as chest pain or palpitations; all 16 had evidence of dysfunction related to the heart. All patients had laboratory evidence of inflammation. Ten patients tested positive for the virus that causes COVID-19 at their initial assessment. Among seven patients with negative viral test results, five had positive antibody test results when first evaluated. Ten patients required intensive care, including three who required mechanical ventilation, and two who died. As the COVID-19 pandemic continues, clinicians and health departments should consider MIS-A in adults with compatible signs and symptoms. Antibody testing might be needed to confirm previous COVID-19 infection, as these patients might not have positive test results from viral or antigen testing.

For more details from this interview, please see the January 2020 issue of Hospital Employee Health.