The latest wave of COVID-19 in Massachusetts has crested, with the number of new cases dropping precipitously since last week, prompting even the most wary prognosticators to see a flicker at the end of the tunnel.
The data indicate the state is headed toward a respite, and the United States as a whole also will see cases decline, said Dr. Jacob Lemieux, an infectious disease specialist at Massachusetts General Hospital. But he cautioned that “every expectation with this virus comes with a caveat because it’s always making us look silly.’’
Data from the Massachusetts Department of Public Health show the seven-day average of new cases is now 30 percent lower than the Jan. 11 peak. But even as the fast-spreading Omicron variant beats a fast retreat, experts are watching an Omicron sibling, dubbed BA.2, that is making inroads in parts of Europe and Israel.
Despite the drop-off in cases, thousands of new infections are still reported daily in Massachusetts, with hospitals overwhelmed by more than 3,000 COVID-19 patients. Hospitalizations seem to be leveling off, but Steve Walsh, president and CEO of the Massachusetts Health & Hospital Association, said hospitals remain “very much in the midst of a COVID-19 peak.’’
“Based on our experience with this virus, we know that even as the number of new cases dip, the resulting hospitalizations do not subside until well after,’’ Walsh said in a statement.
State data released Thursday show that about half the people hospitalized with COVID-19 were admitted for other reasons and happened to test positive for the virus upon admission. But experts noted that even these “incidental’’ cases increase burdens because the patients have to be isolated, and a COVID-19 infection can worsen whatever illness the patient arrived with.
The case numbers mirror reductions of coronavirus measured in waste water, said Stephen Kissler, a postdoctoral researcher studying the spread of infectious diseases at the Harvard T.H. Chan School of Public Health. “I’ve been looking at waste water as my leading indicator,’’ Kissler said.
Coronavirus in waste water started declining in early January, taking the same hairpin turn seen a week later in the state case data. The latest data show the prevalence of the virus back down to levels seen in late December.
COVID-19 cases have long been undercounted, and that problem has likely worsened with the recent popularity of home testing, Kissler said. But, “the current decline in cases probably isn’t just due to a bunch of people switching to at-home testing.’’
Kissler expects cases to continue their downturn, but wonders whether it will plateau at a high level, as happened with Delta.
“I’m not sure what to expect with Omicron but we seem to be through the worst of it, at least in terms of cases,’’ he said, adding that hospitalizations may continue to rise.
Asked what lies ahead, Kissler draped his response in caveats, saying he was “cautiously optimistic’’ that by summer the acute phase of the pandemic would end and the disease would become endemic — meaning it would not go away altogether but could be managed like other health problems.
But Kissler added, “There are lots of endemic diseases that kill hundreds of thousands of people. The transition to endemicity is not a statement of success.’’ He envisions a time when COVID-19 spread will at least be predictable — perhaps requiring the resumption of precautionary measures every winter.
“One of the things that won’t go away is some degree of masking during the winter months,’’ he said.
The months and years ahead may involve a kind of “guerrilla warfare against COVID-19,’’ in which responses will vary based on local conditions, such as the percentage of vaccinated people and elderly people, and the rate of spread in the community, Kissler said.
Others offered an even rosier view. Dr. Ali H. Mokdad, professor of health metrics sciences at the University of Washington’s Institute for Health Metrics and Evaluation, said the next two or three weeks would be difficult in many places. By March and April, however, “We will be in a very good position,’’ he said.
Omicron, he said, is “running out of people to infect.’’ As a result, the variant “is going to end the pandemic phase of COVID-19.’’ The virus will still circulate and mutate, but its effects will be similar to the flu — which also can be quite deadly, taking 52,000 lives in the 2017-2018 season, but which doesn’t restrict activities.
The coronavirus that sparked the pandemic spread easily because the human immune system had never seen it before. But now, even if new variants come along, “We are at a very high level of protection,’’ Mokdad said. “We know it, we have seen it, we’ve been exposed’’ – either through infection or vaccination. Even if we have a surge, a new variant, even if it’s more dangerous than Omicron, we know how to deal with it,’’ he said.
Meanwhile, the mRNA vaccine technology behind the Moderna and Pfizer/BioNTech vaccines will enable manufacturers to quickly target new variants, or perhaps develop a vaccine that will work on any variant, Mokdad said.
Some experts see a day when COVID-19 may cause even milder symptoms. Paul Bieniasz, head of the laboratory of retrovirology at Rockefeller University, said that a “completely plausible’’ and optimistic view holds that the coronavirus will one day join other coronaviruses in causing illnesses such as the common cold.
’’But that is not inevitable,’’ he said, because new variants will undoubtedly emerge. ’’What keeps me awake at night is thinking about what the properties of the next variant will be . . . and how effectively our immune systems will be able to deal with it,’’ he said.
Indeed, researchers are beginning to see the emergence of an Omicron sibling, the subvariant called BA.2, that seems to be growing quickly in Denmark. It’s not yet clear whether BA.2 may be more transmissible and more virulent, or able to better evade vaccines than Omicron.
“What the successive waves have taught us, especially Omicron, is that these variants can change the world in a matter of days,’’ said Lemieux, of Mass. General, who is also co-leader of the viral variants program at the Massachusetts Consortium on Pathogen Readiness.
The Broad Institute of MIT and Harvard, which sequences the genomes of most COVID-19 samples taken in Massachusetts, has detected just a handful of the BA.2 subvariant in Massachusetts, said Bronwyn MacInnis, director of pathogen genomic surveillance. “It seems to be highly transmissible,’’ she said. “It has recently become the dominant strain in several countries, but so far the numbers are low in the US.’’
Dr. Andrea Ciaranello, director of the perinatal infectious disease program at Mass. General, said she remained concerned about the failure to vaccinate people worldwide.
“It’s really important for us to remember that only about 50 percent of the people in the world have had their primary vaccine series and there are huge disparities among countries with some as low as 10 percent,’’ she said Tuesday. “We saw the last couple of variants emerge from largely unvaccinated populations.’’
“We may have gotten a little bit lucky with Omicron, if it turns out to be less severe intrinsically,’’ she said. “We may not get so lucky next time.’’
Felice J. Freyer can be reached at felice.freyer@globe.com. Follow her on Twitter @felicejfreyer.
Kay Lazar can be reached at kay.lazar@globe.com Follow her on Twitter @GlobeKayLazar.
Martin Finucane can be reached at martin.finucane@globe.com.