A new COVID-19 variant known as "Cicada" is spreading to more than 33 countries worldwide. As infections have also emerged in Japan, concerns are growing that existing vaccines may not be effective against it.
Emerging Like a Cicada After Long Dormancy
According to a Nikkei report on Wednesday (local time), the COVID-19 variant "BA.3.2" has been nicknamed "Cicada" because it remains dormant in the body for a long period, like a cicada larva, before reappearing.
Cicada was first reported in South Africa in November 2024. At the time, infections did not increase significantly, and sporadic cases that emerged in Europe in April last year also did not lead to wider spread.
However, infections began to rise sharply from September last year and started spreading in earnest this year. According to the U.S. Centers for Disease Control and Prevention (CDC), infections were detected in at least 23 countries as of February this year, and the number has grown to more than 33 countries as of April.
In Japan, an infection case was found in a specimen from a Tokyo medical institution in January this year. However, since COVID-19 has been classified as a Category 5 infectious disease, similar to seasonal influenza, large-scale testing is not conducted, making it difficult to determine the exact number of infections.
Cicada is drawing attention because of the significant scale of its mutations. According to the CDC, 70 to 75 mutations have been identified in the genetic sequence compared to the previously dominant JN.1 lineage. This means the virus has become genetically quite different from existing strains.
Kei Sato, a virology professor at the University of Tokyo, warned, "There is a high possibility that antibodies generated through vaccination will have difficulty being effective."
He also predicted, "The previously prevalent JN.1 appears to have reached an evolutionary dead end," adding that as its survival became difficult, Cicada may have begun to spread after accumulating major mutations while lying dormant.
"No one imagined it would evolve and emerge without being noticed by anyone," he added.
Pandemic-Level Resurgence Unlikely, but Vigilance Still Required
The World Health Organization (WHO) has designated Cicada as a variant under monitoring. Since COVID-19 tends to spread in two waves during summer and winter, experts expect infections to increase further.
However, the prevailing view is that a pandemic-level spread like that of 2020-2021 is unlikely.
Professor Sato said, "At this point, Cicada does not have the infectivity to replace existing variants worldwide at once." The WHO also stated that there is no data yet showing an increase in severe cases or deaths compared to other COVID-19 variants.
Nevertheless, patients with underlying conditions such as diabetes and hypertension, as well as the elderly, need to exercise particular caution. Since the possibility that Cicada could become more infectious or cause more severe illness through additional mutations cannot be ruled out, experts advise that consistently maintaining basic preventive habits such as hand washing and tooth brushing is important.
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