According to new estimates provided by the Centers for Disease Control and Prevention (CDC), the Omicron subvariants known as BA.4 and BA.5 now account for 13 percent of new coronavirus cases in the United States. This percentage is up from 7.5 percent one week ago and 1 percent at the beginning of May.
The proliferation of the subvariants introduces a new layer of uncertainty into the course that the pandemic will take in the United States, where it is quite probable that the present case numbers are significantly understated. However, it is yet unknown if this will lead to a large new wave of illnesses or an increase in the number of people who end up in the hospital or die as a result.
The latest data, which were announced on Tuesday, are based on modelling, and the projections provided by the CDC have historically been off target. Denis Nash, an epidemiologist at the CUNY Graduate School of Public Health & Health Policy, stated that the overall trend suggests that BA.4 and BA.5 could outcompete the two other Omicron subvariants, BA.2 and BA.2.12.1, which together account for most U.S. cases. BA.2 and BA.2.12.1 together account for the majority of cases in the country.
Data on BA.4 and BA.5, which were found for the first time in South Africa in the beginning of 2022, are still very restricted. However, these variations seem to disseminate more rapidly than previous forms of Omicron, such as BA.2, and they may be more adept at evading the immune system’s defences. Even though more research has to be done, there is not much evidence to suggest that they cause diseases with a more severe course.
Despite significant pre-existing protection to the virus, the BA.4 and BA.5 subvariants contributed to an increase in the number of cases in South Africa during the months of April and May. According to Jeffrey Shaman, an infectious disease epidemiologist at Columbia University, the wave was not as significant as the nation’s prior waves, and the number of fatalities did not jump by as much as they had in previous waves.
“In what ways is it comparable to us?” he questioned. Another wave, fuelled by BA.4 and BA.5, is something that “I believe it’s plausible that we may witness.” However, if the United States were to follow South Africa’s lead — which is not a certainty — the wave may be less severe than prior surges and lead to less significant rises in the number of people admitted to hospitals and those who passed away, he said.
According to a database maintained by The New York Times, the United States has been averaging approximately 100,000 new cases a day over the last three weeks. This number is much higher than the less than 30,000 cases that were reported in late March.
And even if hospitalizations have started falling in the Northeast, they are on the rise in other parts of the country. Less certain are the trends in the number of new fatalities, which over the last month have ranged from around 250 to 400 a day; nonetheless, the statistic is averaging significantly lower than it was during the winter Omicron spike.
The most current statistics imply that BA.4 and BA.5 still constitute a very modest fraction of cases worldwide; however, this may alter in the weeks that are to come. In a study that was published not too long ago, the United Kingdom’s Health Security Agency made the observation that the two subvariants were replacing BA.2 in many nations at a rate that was comparable to the rate at which BA.2 had replaced the first version of Omicron.
In recent years, new subvariants have been making significant headway in the United States. In the week that came to a conclusion on June 4, BA.5 was responsible for an estimated 7.6 percent of cases, while BA.4 was responsible for 5.4 percent of cases. This is an increase from the previous week, when those percentages were, respectively, 4.2 percent and 3.3 percent.
In some regions of the southern United States, the subvariants have attained a particularly widespread prevalence. According to the newly released statistics, BA.4 and BA.5 are responsible for more than one out of every five infections in the area that includes Arkansas, Louisiana, New Mexico, Oklahoma, and Texas.
The distribution of the subvariants is further shown by the data from wastewater. In the state of Missouri, for example, BA.4 and BA.5 were discovered in a limited number of the state’s sewersheds around the beginning of May. Sewersheds are geographical regions in which all of the wastewater flows into a single treatment facility or other collection site. Marc Johnson, a virologist at the University of Missouri who has been testing the wastewater throughout the state, said that the subvariants are now detected in more than half of them.
Preliminary data from laboratory study shows that unvaccinated patients who were infected with the first form of Omicron, also known as BA.1, could be readily reinfected with BA.4 or BA.5 if they are not protected by vaccination.
This immunological evasiveness, along with the natural decline in resistance to infection that occurs over time, would explain why the most recent subvariants have been able to spread so rapidly.
