FRIDAY, May 1, 2020 (HealthDay News) -- The severity of COVID-19 illness may be influenced by what researchers call "cytokine storms."

In a new study, investigators assessed 522 COVID-19 patients, aged 5 days to 97 years, who were admitted to two hospitals in Wuhan, China, in December and January. The study also included a "control group" of 40 healthy people.

Compared to the control group, 76% of COVID-19 patients had significantly lower levels of T cells -- a type of white blood cell that plays a crucial role in immune response against viral infections.

Patients admitted to the intensive care unit had much lower T cell counts than those who didn't require ICU care. Patients over age 60 had the lowest T cell counts, the findings showed.

And the T cells that did survive in COVID-19 patients were exhausted and unable to function at full capacity, the study authors said.

Read the full HealthDay story.