Two new COVID variants, BA.4 and BA.5, are spreading in CT

Connecticut’s COVID-19 numbers have improved in recent weeks after a surge driven by the BA.2 subvariant, but that doesn’t mean the state is clear now.

In fact, experts say, the next threat may already have arrived.

According to researchers tracking COVID-19 strains in Connecticut, subvariants BA.4 and BA.5, descendants of the Omicron variant, are already circulating in significant numbers with the potential to cause a further increase in illness and death .

“Anytime something new comes up, it’s kind of bad news because it means what comes up is more appropriate than what’s here,” said Nathan Grubaugh, a professor at the Yale School of Public Health, closely tracking variants in the state. “The magnitude of this bad news depends on many different contexts.”

Here’s what you should know about BA.4 and BA.5 in Connecticut.

What distinguishes these variants from previous varieties?

BA.4 and BA.5 are more contagious than existing variants—including BA.2 and BA.12.1, which were prevalent in Connecticut—and appear to evade both vaccine and natural immunity to a greater degree than previous variants.

That means people who contracted COVID-19 last winter are likely vulnerable to being reinfected by the new strains, and even those who had the disease this spring could be at some risk.

“People who are counting on, ‘I’ll be off for a few months now because I have COVID,’ are not true,” said Dr. Ulysses, chief epidemiologist at Hartford HealthCare.

Although the BA.4 and BA.5 have slightly different lineages, experts say they are similar enough to be considered together for most purposes.

How common are these variants in Connecticut?

BA.4 and BA.5 accounted for about 20 percent of Connecticut’s COVID-19 cases as of June 3, according to Grubaugh’s lab, and likely account for about half of the state’s transmission today. At the rate they are currently spreading, Grubaugh said they will almost certainly dominate Connecticut for the coming weeks.

BA.4 and BA.5, first identified in South Africa last winter, have since spread across the United States and account for at least a quarter of cases nationwide, according to the Centers for Disease Control and Prevention.

Grubaugh said this spring he wasn’t sure if the BA.4 and BA.5 would displace BA.12.1 in Connecticut, but as the variants become more widespread, it’s becoming increasingly clear what’s happening.

What has this meant for the spread of COVID-19 in Connecticut?

There is already some evidence that BA.4 and BA.5 are causing some additional infections in Connecticut. While cases and the test positivity rate fell quickly in late May and early June, that trend appeared to be slowing this week.

“If you look at the case numbers, they’re already coming down a lot faster than I was hoping,” Grubaugh said. “Obviously the drop in cases that we’ve seen week in and week out here over the past few weeks has been great news, but this week’s [numbers] are not that different from last week.”

As of Friday, Connecticut had registered 3,698 cases over the past week — not counting home testing, which isn’t reported to public health officials — with a positivity rate of 8.1 percent. Both numbers are lower than April and May but higher than earlier this week.

At a time of year when low spread of COVID-19 was expected, it instead remains fairly high.

“This is the highest number of cases we have ever had [in June] in the three years of the pandemic,” Grubaugh said. “This is the worst June yet in terms of cases. Maybe not in terms of hospitalizations and deaths, but in terms of cases it’s the worst June yet.”

What could these new variants mean for Connecticut’s future?

BA.4 and BA.5 have already caused a significant surge in COVID-19 in South Africa, and experts say it’s possible the same thing will happen in the northeastern United States.

Nonetheless, warns Dr. David Banach, hospital epidemiologist at UConn Health, before direct comparisons with other countries.

“Populations are different, so the transmission seen in South Africa may look different than what we’re seeing here in the Northeast,” Banach said. “Also, the impact of previous infections has been different for each country and how that would affect future increases in cases and variants also plays a role. And I still think there is a seasonal component and seasonality might look different in South Africa than here in the North East.”

Grubaugh said his “pessimistic side” is worried about another surge, but it’s too early to know if it’s really imminent.

Wu predicts that BA.4 and BA.5 will “cause a bit of trouble” in Connecticut, perhaps keeping transmission relatively high when it might otherwise drop.

“They will soften our descent,” Wu said. “That’s probably why we have this sawtooth pattern [in the state COVID numbers] – one day up, one day down. I believe [the variants are] contribute to that to some extent.”

Despite his general concern, Grubaugh was able to deliver some good news: While in previous waves, another variant would often be spreading elsewhere in the world, just waiting to arrive in the US, as there are currently no other obvious threats on the horizon.

“At the moment there is nothing else that stands out in particular.” said Grubaugh. “If we can get through BA.4 and BA.5 without a wave, we might have a time when things will calm down a bit.”

[email protected]

Leave a Comment