Connecticut continues to see a decrease in the coronavirus. On Thursday, the state announced that just 2.02 percent of the COVID tests administered were positive for the virus.

That’s an ever-so-slight uptick from Wednesday, but the positivity rate in Connecticut hasn’t been this low since mid-October.

“The numbers are all trending in the right direction and I’m not sugarcoating it,” Gov. Ned Lamont said during his Thursday briefing. “It’s good news.”

Hospitalizations are down, and though there were 20 new reported deaths associated with the virus, Lamont said it’s lower than it was only a few weeks ago.

“Even that lagging indicator is showing some good news,” he said.

The question is, why?

“It is a good question without a clear answer,” said Pedro Mendes, who works as a disease modeler for UConn’s Center for Quantitative Medicine.

There are a few possible factors to consider, the first being the question of immunity, though Mendes said he believes “we can assume, with a high degree of certainty, that this is not yet herd immunity.”

It’s possible that older adults and nursing home residents might be seeing a measure of vaccine-conferred immunity, Mendes said.

There were 483 coronavirus cases in Connecticut nursing homes on Jan. 15. On Thursday, it was 30, a dip likely attributable to the high rate of vaccination in nursing homes. But that wouldn’t account for the steep drop in infections the state is seeing, according to Mendes.

“For the general population, there isn't yet much ‘herd immunity’ effect,” he said. “I think that will start having an impact when we get closer to 50 percent vaccination.”

Catching the virus does confer some immunity, though how much and for how long is “very variable,” Mendes said, dependent in part on the severity of infection.

Connecticut has so far administered at least one dose of vaccine to 14 percent of the population. As of Thursday, 271,903 people in Connecticut have tested positive for the coronavirus, but Richard Martinello estimates that as many as 25 percent of the state’s 3.56 million residents have been infected.

“We have a long way to go before we achieve herd immunity,” said Martinello, medical director for infection prevention at Yale-New Haven Hospital.

There’s also the question of winter. The cold, snowy weather may be helping to encourage social distancing guidelines.

“We're, quote, ‘flattening the curve’ with the use of non-pharmaceutical interventions,” Martinello suggested.

Seasonality is also a possibility. Science is still not sure if infections from the coronavirus are rooted in seasonal weather shifts, what Martinello called “still a big unknown.”

“It's too early to call,” he said. “We're going to have to wait and see when this pandemic settles out, when we've achieved herd immunity, then we have to study the epidemiology of the virus to better understand how or how not seasonality impacts it.”

Within the question of seasonality may be the best available answer to the question of why COVID numbers in Connecticut — and in the rest of the country — are dipping so deeply.

There is, Martinello said, a natural ebb and flow to diseases like the coronavirus. They come and go in waves, and “there's really not a good understanding of why waves occur,” he said.

Connecticut is on the back end of its second coronavirus wave. There was a peak toward the end of April, and then some respite until December. On Thursday, the state announced a decrease of 16 hospitalizations, for a total of 568 people battling COVID in Connecticut hospitals.

There were more than 1,000 patients in the hospital with COVID-19 throughout December, up until the end of January.

“I think the slowing down of cases is mostly due to the ‘holidays effect’ being over now,” Mendes said. “A large factor in this recent surge was travel and higher risk-taking in the Thanksgiving-Christmas-New Year season. We're now over a month after that and that's why we are seeing lower cases. The actual decrease in hospitalizations started in early January and it has continued since then.”

Why those waves occur, and why they do not seem to match with the shift in seasons, is not fully known, according to Martinello. It’s not specific to just COVID, but a dynamic seen in most respiratory diseases.

“Why do we see it go away, come back, and then go away?” he asked. “Typically, if we didn’t have vaccination, these waves would continue, presumably, until we achieve that degree of herd immunity.”

The bad news is, if we don’t see huge swaths of people vaccinated, it’s possible Connecticut could see a third wave.

“If we're seeing the downslide of the second wave, this is the time to get vaccination out,” Martinello said. “So that when and if that third wave does start, we have a much more protected population, so we're going to really mitigate the impact of that third wave.”

In Connecticut, there has been one reported case of the B.1.351 coronavirus variant initially identified in South Africa, and 42 cases of the B.1.1.7 variant first found in the United Kingdom, both of which are potentially more transmissible than the original strain.

“We shouldn't take too much solace yet," said Andy Slavitt, a senior adviser to President Joe Biden’s COVID-19 response team, who specifically expressed concern about the two variants.

“What happens with these variants, they tend to grow before you can see that they're growing,” he said.

But that, Mendes said, is why it’s so important to vaccinate as many people as possible.

“The good news is that the lower we can get in infections and hospitalizations before the B.1.1.7 starts becoming widespread, the better we can weather the likely new surge of infections that will cause,” Mendes said.

Connecticut Media Group