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These omicron subvariants could be the most infectious human viruses, expert says

Each person infected with omicron subvariants BA.4 or BA.5 can pass the virus to about 18 others. This is more contagious than any other human virus

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An illustration of the omicron variant.

Illustration by Michelle Budge, Deseret News

For decades, measles has taken the title of the most contagious virus among humans. However, new subvariants of the omicron strain of COVID-19 could take that title, according to Adrian Esterman, an Australian professor who specializes in biostatistics and epidemiology.

Breaking down the news: The new strains of omicron — BA.4 and BA.5 — are far more transmissible than the earlier variants of COVID-19, the Deseret News has previously reported.

  • When COVID-19 first emerged in 2020, its transmission rate was relatively low compared to most other viruses. However, with each new variant, the virus is becoming more and more contagious.
  • The original strain of COVID-19 had a reproductive rate — formally known as Ro or R- naught value — of around 3.3. This means that on average, an infected person infected three other people, according to Fortune.

  • The newer omicron subvariants have infection rates that have skyrocketed past most human viruses. BA.4 and BA.5 have reproductive rates of around 18.6, which is tied or slightly higher than measles — Ro 18 — and mumps — Ro 12.

The future of omicron: Experts believe that omicron is not done yet. According to the Deseret News, a new subvariant is making its way around the world: BA.2.75, also known as “centaurus.”

  • Scientists say that it is still too early to determine whether or not this subvariant will be more contagious or harmful than BA.4 and BA.5, per Time magazine.
  • However, the new subvariant is still spreading quickly, according to MedPage Today. So far, BA.2.75 has made an appearance in 10 countries across Asia, Europe, Australia and North America.
  • Marc Johnson, a professor of molecular microbiology and immunology at the University of Missouri’s School of Medicine, said that vaccines will still work against BA.2.75, but that they will provide protection “even less than before.”