Characteristics of the omicron variant

The Yomiuri Shimbun

Question: What are the characteristics of the omicron coronavirus variant?

Answer: According to an analysis by researchers from the University of Tokyo and elsewhere in Japan, cases in Britain and South Africa indicate the infectivity of the variant is three to five times higher than that of the delta variant, which was prevalent in Japan last summer.

Data from the United States shows that the incubation period of the virus is about three days, shorter than that of the delta variant at about four days, and the number of cases can increase swiftly.

The omicron variant has about 30 mutations in proteins on the surface of the virus, half of which are in areas that attach to human cells. The mutations may have made it easier for the virus to invade human cells compared to the delta variant.

Q: What are the symptoms?

A: According to an analysis of 50 omicron patients diagnosed in Okinawa Prefecture before Jan. 2, 75% had a fever of 37.5 C or higher; 60% had a cough; 52% fatigue; 46% sore throats; 38% a runny or stuffy nose; 33% headaches; 8% difficulty breathing; and 2% taste and smell disorders.

A doctor in the prefecture said omicron symptoms are more similar to those of influenza than to those of previous types of the coronavirus.

Q: Is it unlikely to cause serious illness?

A: In an experiment conducted by the University of Hong Kong, omicron multiplied 70 times faster than the delta variant in bronchial tubes but grew 10 times slower in the lungs.

In animal experiments, pneumonia seems to be less likely to occur. In Britain, the risk for hospitalization was 50%-70% lower than that of the delta variant as of late December.

Q: Should we be worried?

A: It is unclear whether the small number of severe cases is due to the weak pathogenicity of the disease or to protection from vaccines or past outbreaks, but we must remain vigilant.

The novel coronavirus often causes long-term effects such as fatigue and breathlessness even in mild cases, but the long-term effects of the omicron variant are largely unknown.

As the number of cases increases, the number of severely ill people will naturally increase. People should continue following basic measures such as washing their hands, wearing masks and avoiding the so-called Three Cs of closed spaces, crowded places and close-contact settings.