Enlarge / WHO's COVID-19 technical lead, Maria Van Kerkhove, looks on during a press conference at the World Health Organization's headquarters in Geneva, on December 14, 2022. (credit: Getty | FABRICE COFFRINI )

With global attention and anxiety locked onto the latest coronavirus omicron subvariant BA.2.86, health officials and experts are still mostly in the dark about how the highly mutated virus will play out.

At the start of the week, amid a flurry of headlines, researchers had only six genetic sequences of the virus in the public repository GISAID, even though the virus had already spread to at least four countries (Denmark, Israel, UK, and the US). As of the time of publication of this article on Friday, there are still only 10 sequences from five countries (Denmark, Israel, UK, US, and South Africa). According to the World Health Organization, the variant has also appeared in wastewater sampling from Thailand and Switzerland.

As Ars reported Monday , BA.2.86 gained attention for having a large number of mutations compared with BA.2, the omicron subvariant from which it descended. The number of mutations in BA.2.86's critical spike protein is over 30, rivaling the number seen in the original omicron subvariant, BA.1, which went on to cause a tidal wave of cases and hospitalizations. BA.2.86's spike mutations appear geared toward evading neutralizing antibody protections built up from past infections and vaccinations. But with such scant and spotty detection, it's impossible to say whether this variant can outspread its many omicron-subvariant cousins to cause a wave of infection. It's also still not possible to determine if it can cause more severe disease than other variants. So far, severe disease symptoms have not been reported from the 10 cases—but that is not enough data to draw any conclusions. As the Centers for Disease Control and Prevention reported in a risk assessment Wednesday, it's " too soon to know " the impact of BA.2.86 on transmission and disease severity.

Enlarge / Revelers celebrate New Year’s Eve in Times Square on January 1, 2023, in New York City. This year's New Year's Eve returned to pre-COVID-19 pandemic numbers, with around 1 million people estimated to fill Times Square. (credit: Getty | Alexi Rosenfeld )

A new omicron coronavirus subvariant dubbed XBB.1.5 now accounts for an estimated 40.5 percent of all US COVID-19 cases amid a winter wave that is driving up hospitalizations, particularly in places where XBB.1.5 is most prevalent.

Nationwide, new reported cases are hovering around 59,000 per day, which is still relatively low compared with previous waves. But case data has become murkier over the 3-year-old pandemic, with fewer testing sites available now and the results of common at-home tests going unreported. Additionally, data reporting generally lags around end-of-year holidays, meaning case reports may jump in the coming days as backlogged data rolls in.

Hospitalizations, however, are clearly rising, with an average of around 45,000 hospitalized per day, according to data tracking by The New York Times. National hospitalization rates now rival those from the peak over this past summer driven by bygone omicron subvariants, federal data shows. Some of the areas seeing the large upticks in hospitalizations are those where the new subvariant, XBB.1.5 is most prevalent. For instance, in the Northeast (federal health region 1), XBB.1.5 has the highest regional proportion, accounting for 75 percent of cases, and hospitalizations have risen 16 percent over the prior seven days, the largest region-specific rise, according to data from the Centers for Disease Control and Prevention.

Dans son dernier avis, le Conseil scientifique Covid-19 imagine 3 scénarios pour la suite de l'épidémie de coronavirus cet automne.

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The swift rise of omicron subvariant BA.5—with its increased immune-evading abilities and demonstrable growth advantage—has federal officials on edge. In a flurry of activity late Monday and early Tuesday, officials doubled down on pandemic measures, renewed calls for vigilance, and are considering expanding eligibility of second boosters to all adults.

In a press briefing Tuesday morning, White House COVID-19 Response Coordinator Ashish Jha outlined a battle plan against BA.5 , which, as of today, is estimated to account for 65 percent of cases in the US . Jha highlighted efforts and tools to prevent another towering wave of infection as seen with the original omicron in January. The plan includes a stronger push to get Americans vaccinated and boosted, plus renewed encouragement to test, treat, mask, and improve indoor ventilation.

US COVID-19 cases are currently plateaued at a high level of around 117,000 new cases per day—but that's likely a significant underestimate given that many Americans are testing at home and not reporting their cases. Hospitalizations and intensive care admissions , meanwhile, are rising, with 17 percent and 21 percent increases over the past two weeks, respectively, according to tracking by The New York Times. Generally, the daily average of hospitalizations has more than doubled since the end of May, with the current average nearing 38,000.

Enlarge / A person holds a positive SARS-CoV-2 rapid test on February 17, 2022 in Berlin, Germany. (credit: Getty | Thomas Trutschel )

Omicron subvariant BA.2.12.1 has overtaken BA.2 as the dominant version of the pandemic coronavirus in the US, now accounting for an estimated 59 percent of cases nationwide . But BA.2.12.1's reign may end as quickly as it began, with yet another batch of omicron subvariants gaining ground—BA.4 and BA.5—and threatening to cause more breakthrough infections.

BA.2.12.1 has a transmission advantage over BA.2, which itself has an edge over the initial omicron subvariant, BA.1, that caused a towering surge of US cases in mid-January. BA.2 peaked in mid-April, accounting for 76 percent of US cases at its height. But then came BA.2.12.1 , which is named for being the 12th lineage stemming from BA.2 and the first branch of that BA.2.12 lineage.

When BA.2 peaked in mid-April, BA.2.12.1 accounted for about 18 percent of cases. It reached about 43 percent prevalence by mid-May and has since overtaken BA.2, which currently accounts for only about 35 percent of cases. BA.2.12.1 is dominant in every region of the country, except for the Northwest, according to the Centers for Disease Control and Prevention.

Enlarge / The Comirnaty (Pfizer/BioNTech) and Moderna COVID-19 vaccines. (credit: Getty | Marcos del Mazo )

People ages 60 and older who were initially vaccinated with two Pfizer-BioNTech COVID-19 vaccine doses were better protected from the omicron coronavirus variant after being boosted with a Moderna vaccine rather than another dose of the Pfizer-BioNTech vaccine.

Those results are according to interim data from a small but randomized controlled clinical trial in Singapore and published this week in the journal Clinical Infectious Diseases.

The study—involving 98 healthy adults—can't determine if the Moderna booster is simply superior to a Pfizer-BioNTech booster for older adults or if a mix-and-match booster strategy is inherently better. It also focused solely on antibody levels, which may or may not translate to significant differences in infection rates and other clinical differences. It also only followed people for 28 days after a booster, so it's unclear if the Moderna booster's edge will hold up over time.

Enlarge / People watch a television broadcast showing a file image of North Korean leader Kim Jong Un during a military parade at the Seoul Railway Station on May 4, 2022, in Seoul, South Korea. (credit: Getty | Chung Sung-Jun )

North Korea instituted a nationwide lockdown Thursday after reporting an omicron coronavirus variant outbreak in its capital, Pyongyang. The report marks the first time during the pandemic that the secretive, authoritarian country has acknowledged coronavirus cases within its borders, though outside experts have doubted the country's previous claims of zero infections.

Acknowledging omicron cases in Pyongyang raises questions over whether the admission is a sign of deteriorating public health conditions and/or a signal that the country is willing to accept pandemic aid, including vaccines.

So far, North Korea's government has rejected offers of COVID-19 vaccine supplies from the United Nations' global vaccination effort, COVAX, and China's domestically produced vaccines. North Korea is one of the few countries that has not run a public vaccination effort, and its 26 million people are believed to be largely unvaccinated.