Is the BA.2 subvariate in Ómicron as contagious as measles?

For several weeks, new COVID-19 cases have increased in China, Australia, and some European countries. And all the blame fingers point to the subvariate of Ómicron BA.2 as the driving force for the outbreak.

The high contagiousness of the subvariate, along with the fact that measures to prevent the disease have eased worldwide, has now become a combo that worries health authorities.

Now, according to Adrian Esterman, an Australian epidemiologist and worldwide health organization (WHO) official, everything says BA.2 is “as contagious as measles.” The professor said that the subvariate is 40% more contagious than the original variant of SARS-CoV-2.

And, noting that the basic reproductive number (R0) would be around 12, he stressed that “if it was allowed to spread uncontrollably, each infected person would transmit it to 12 others.”

“This will make the temperament five times more contagious than the original Wuhan virus, and it is one of the most contagious diseases known to science,” he argues.

According to the British newspaper Daily Mail, the statement would explain why the mutant virus was able to undermine China's “zero COVID” policy, which surpassed the original strain in the UK in about a month and so far succeeded in suppressing all versions of the virus.

Explaining his theory, Professor Esterman explored: “The default replication number (R0) for BA.1 is about 8.2, which means that BA.2 has an R0 of around 12. This brings us very close to measles, the most contagious disease we know.”

The R0 number is the average number of people that each BA.2 patient can become infected if the population is immune (vaccination coverage is high) or there are no behavioral changes.

However, most scientists say that there is no reason to worry about the variant. Because “the cases that cause them are as mild as the original Omicron.”

According to official estimates, the BA.2 subvariate currently lags behind almost all cases in the UK, accounting for 83% of infections last week alone.

This accounts for 52% of all infections until February 20 after becoming dominant 3 weeks ago.

The National Bureau of Statistics (ONS) estimates that COVID-19 cases in the UK have increased since mid-February, and estimates that 1 in 25 people in the UK were infected last week.

Scientists estimate that the R0 of the original Wuhan strain of SARS-CoV-2 is about 2.5. However, the R0 of measles, which is one of the most contagious viruses studied by science, ranges between 12 and 18.

Experts estimate that the number corresponding to chickenpox is the region of 10-12. Even if BA.2 has an R0 of 12, it does not mean that everyone infected with BA.2 will transmit the virus to 12 other people.

The actual R-rate, which reflects how quickly an outbreak increases or shrinks, is always much lower than R0. This is because it takes into account real-world data that can easily distort the forms of disease outbreaks, such as population immunity.

Cases, hospitalizations, and deaths are rapidly increasing due to the emergence of BA.2 in Hong Kong, where the acceptance of vaccines has been reduced due to the early success of government policies on virus control.

Professor David Livermore, a microbiologist at the University of East Anglia, said that “it may be” that R is actually 12 in a population that does not have immunity to the virus.

However, he emphasized that because the virus has reached every corner of the world, these populations do not currently exist almost anywhere in the world.

When people asked if they should be interested in BA.2, Professor Livermore felt it wasn't. “I think the virus is simply buried in the population.” And it seems that BA.2 does not have a higher capacity to cause serious illness than the classic Omicron.”

Meanwhile, Julian Tang, a specialist in respiratory science at the University of Leicester, said estimates of respiratory viruses are “quite high”, if not impossible.

In Denmark, where BA.2 dominates in recent weeks, officials lifted restrictions in February stating that the virus no longer poses a “deadly threat”.

Daily COVID cases in the UK began to increase in early March, shortly after BA.2 became dominant in the UK.

In this regard, Professor Mark Woolhouse, a member of the British Scientific Advisory Group (SAGE) and an epidemiologist at the University of Edinburgh, told Forbes magazine last week that: “In my opinion, this is the most important factor in the recent increase in cases. Hospitalization in the UK is an increase in the subvariate BA.2 Ómicron.

Therefore, experts are not ready to say with certainty that the new major wave of COVID is on the global horizon or causes for immediate concern; rather, they think it is time to be vigilant and act preventively.

Dr. Gavin Yamey, professor of global health and public policy at Duke University, said: “We must take the opportunity currently offered by the pause to prepare for a possible wave of additional or transformation concerns. To do this, we need to “expand the scope of vaccination and booster applications and provide free access to high-quality masks and rapid testing.”

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