Omicron variant replicates less at high-fever condition, researchers say

Researchers say the Omicron variant of the coronavirus replicates less at high-fever temperature than at normal human body temperature.

The study published in the international science journal Lancet Microbe was conducted by a group of scientists mostly in Japan. They include Project Professor Kawaoka Yoshihiro from the Institute of Medical Science, University of Tokyo, and Professor Noda Takeshi from Kyoto University.

The group incubated the Delta variant and the Omicron BA.5 and BQ.1.1 subvariants on lung cells generated from human induced pluripotent stem cells. They observed the growth of viruses at two different temperatures -- normal body temperature of 37 degrees Celsius and elevated temperature of 40 degrees.

The three variants showed similar growth at 37 degrees in two days, increasing to 100,000 to 1 million times their original figures.

At 40 degrees, the Delta variant showed growth similar to that at 37 degrees. But the BA.5 increased to only 1,000 times, and the BQ.1.1 did not replicate.

The researchers say elevated body temperature during illness might restrict the Omicron variant's replication in the lungs and could have an important role in limiting illness severity compared to infection with the Delta variant.

Kawaoka said 40-degree temperature also restricts replication of the seasonal flu virus. He added that the characteristics of the coronavirus may have changed over the past three years.