Omicron subvariants known as BA.4 and BA.5 now account for 13% of new coronavirus cases in the United States, increasing from 7.5% a week ago to 1% in early May. .. According to a new quote From the Centers for Disease Control and Prevention.
The spread of subvariants adds further uncertainty to the pandemic trajectory in the United States, where the current number of cases is likely to be significantly underestimated. But it’s unclear whether it will lead to a major new wave of infection or a surge in hospitalizations and deaths, scientists warned.
The new numbers released on Tuesday are based on modeling, and the CDC estimates were previously unmarked. However, the overall trend suggests that BA.4 and BA.5 may outperform the other two Omicron subvariants, BA.2 and BA.2.12.1. Epidemiologist at CUNY Graduate School of Public Health and Health Policy.
“This can happen very quickly,” said Dr. Nash.
The BA.4 and BA.5 data first detected in South Africa in early 2022 remain limited. However, these variants appear to spread more rapidly than previous versions of Omicron, such as BA.2, and may be better at dodging immune system defenses. So far, more research is needed, but there is little evidence that they cause more serious illnesses.
“How similar is it to us?” He said. “I think we may see another wave” fueled by BA.4 and BA.5. But if the United States follows South Africa’s example (which is not a guarantee), the waves are milder than the previous surge and can cause an inconspicuous increase in hospitalizations and deaths, he said.
In the past few weeks, the United States has averaged about 100,000 new cases per day, up from less than 30,000 in late March, according to the New York Times database.
Globally, the latest data suggest that BA.4 and BA.5 still represent a relatively small proportion of cases, which may change in the coming weeks.of Recent reportsUK Health and Security Agency points out that in many countries, two subvariants are replacing BA.2 at about the same speed that BA.2 replaced the original version of Omicron. Did.
New subvariants are well established in the United States. During the week ending June 4, BA.5 accounted for an estimated 7.6% of cases and BA.4 accounted for 5.4% of cases, up from 4.2% and 3.3% in the previous week, respectively.
Subvariants have become especially common in parts of the southern United States. In regions including Arkansas, Louisiana, New Mexico, Oklahoma, and Texas, BA.4 and BA.5 account for more than one in five infections, according to new figures.
Wastewater data also highlights the spread of subvariants. For example, in Missouri in early May, BA.4 and BA.5 appeared in a small number of state sewage treatment plants, or in geographical areas where wastewater was supplied to a single treatment plant or other collection point. .. Mark Johnson, a virologist at the University of Missouri who analyzes state wastewater, says subvariants are now detectable in more than half of them.
Reserve Evidence from laboratory studies Unvaccinated people infected with the original version of Omicron, known as BA.1, suggest that they can easily be re-infected with BA.4 or BA.5. (Research suggests that vaccinated people are more likely to be somewhat successful.)
This antigenicity may explain why the latest subvariants were able to spread so quickly, in addition to the natural decline in defense against infection over time.
Sarah Kahalan Contributed.