Enlarge / A passenger wearing protective clothing amid the COVID-19 pandemic waits to board a domestic flight at Shanghai Pudong International Airport on January 3. (credit: Getty | HECTOR RETAMAL / AFP )

Although China has largely abandoned COVID-19 case reporting, evidence of its massive wave of infection readily shows up in airports outside its borders.

On a December 26 flight from the southeastern city of Wenzhou to Milan, Italy, 42 percent of the 149 passengers on board tested positive for COVID-19 upon arrival, according to a study published Thursday in the journal Eurosurveillance .

The Italian researchers behind the study also looked at test-positivity rates of three other flights from eastern cities in China to Italy, two to Milan and two to Rome, all at the end of December. Collectively, 23 percent of the passengers from the four flights (126 of 556 passengers) were positive for SARS-CoV-2. The other three flights had positivity rates of 19 percent, 11 percent, and 14 percent.

Enlarge / A CDC COVID-19 variant testing site inside Tom Bradley International Terminal at Los Angeles International Airport on Monday. The airport testing is part of the government's early warning system for detecting new variants, which began expanding recently in the wake of a COVID-19 surge in China. (credit: Getty | Jill Connelly/Bloomberg )

Amid a winter wave of COVID-19 in the US, the latest coronavirus omicron subvariant, XBB.1.5, has grabbed headlines due to its swift rise, raising fears of another towering spike in the disease. But the spotlight is revealing more questions than answers in the early days of the subvariant, which has ominously been described as one of the most immune-evasive omicron subvariants to date.

Last week, the US Centers for Disease Control and Prevention quietly downgraded estimates of its prevalence. As Ars and other outlets reported, the CDC previously estimated that XBB.1.5 accounted for 40.5 percent of COVID-19 cases throughout the country in the week ending on December 31, with the highest prevalence in the Northeast. But last Friday, the agency updated the estimates with a backlog of sequencing data from over the holidays, which indicated XBB.1.5 accounted for 18 percent of cases nationwide that week—not 40.5 percent. Currently, the CDC estimates that XBB.1.5 accounted for 27.6 percent of cases nationwide in the week ending on January 7. But the 95 percent prediction interval is wide, spanning 14 percent to 46.5 percent).

The updated estimate still indicates that the variant, first detected in New York in October, is on the rise. But the uncertainty throws a wrench in estimates of its transmission advantage over other omicron subvarianty, BQ.1.1 is still the most prevalent omicron subvariant, accounting for an estimated 34 percent of cases in the US.

Enlarge / An elderly female patient with COVID-19 is treated at No. 2 People's Hospital of Fuyang City in China. (credit: Getty | Sheldon Cooper/SOPA Images/LightRocke )

With China's zero-COVID policy abruptly scrapped last month, the pandemic virus is now ripping through the country's population, and health experts are bracing for a wave of devastation as peak transmission shifts from urban centers to more vulnerable rural communities. The dire situation is expected to be "dramatically enhanced" by mass travel later this month for celebrations of the Lunar New Year on January 22.

Multiple modeling studies have suggested that China could see around 1 million deaths in the coming weeks as the country reopens amid a raging outbreak. Last month, modeling by The Economist estimated that 96 percent of China's 1.4 billion people could catch the virus within the next three months, resulting in 1.5 million deaths . Of those deaths, 90 percent would be among people aged 60 and over.  Another modeling study, partly funded by China's Centers for Disease Control and Prevention, also estimated that 957,600 would die in the coming weeks if the country doesn't swiftly roll out fourth-dose COVID-19 vaccines.

Because China was previously able to keep COVID-19 waves at bay with its zero-tolerance policies, most of the country's immune protection derives from vaccination rather than prior infection or hybrid protection. Around 90 percent of China's population has had two shots of COVID-19 vaccines, but fewer than 60 percent have received a third shot as a booster dose. And even for those who have gotten a third dose, many of those doses were taken months ago, and peak protection has passed. Vaccination coverage among the elderly is particularly worrying. About 30 percent of people aged 60 and over have not gotten a third dose, and for people aged 80 and over, a startling 60 percent have not gotten a third dose.

Enlarge / Symptoms of long COVID-19 include fatigue, shortness of breath and cognitive issues. (credit: Getty Images / ArtistGNDphotography)

The Research Brief is a short take about interesting academic work.

The big idea

Even mild COVID-19 cases can have major and long-lasting effects on people’s health. That is one of the key findings from our recent multicountry study on long COVID-19–or long COVID–recently published in the Journal of the American Medical Association.

Long COVID is defined as the continuation or development of symptoms three months after the initial infection from SARS-CoV-2, the virus that causes COVID-19. These symptoms last for at least two months after onset with no other explanation.

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.

Enlarge / An intensive care nurse cares for a patient suffering from respiratory syncytial virus (RSV), who is being ventilated in the children's intensive care unit of the Olga Hospital of the Stuttgart Clinic in Germany. (credit: Getty | picture alliance )

With SARS-CoV-2 still circulating and seasonal viruses, including influenza and RSV, making up for lost time during the pandemic, the US is getting slammed by respiratory illnesses. And things could get worse as more holidays and associated gatherings approach, health officials warned Monday.

"This year's flu season is off to a rough start. Flu's here, it started early and with COVID and RSV also circulating, it's a perfect storm for a terrible holiday season," Sandra Fryhofer, chair of the American Medical Association and adjunct medicine professor at Emory University School of Medicine, said in a press briefing held by the Centers for Disease Control and Prevention today. "Over the last few years, COVID-protective measures also prevented spread of flu and other respiratory infections, but we're really no longer in that bubble."

Cases of influenza-like illnesses (ILIs) are soaring throughout the country , with 47 states seeing "very high" or "high" activity levels, according to the latest CDC data. The agency estimates that there have been at least 8.7 million illnesses, 78,000 hospitalizations, and 4,500 deaths from flu.

Enlarge / Runner in Shanghai, China. (credit: Getty| Avalon )

In the early morning of August 16, a 41-year-old man in China's southwest-central municipality of Chongqing got up and went for a jog along a lake in a local outdoor park—something that should have been a pleasant, if not unremarkable, outing. But what really happened during that 35-minute jaunt has now sparked international alarm and debate, with some scientists doubtful of China's startling account.

According to the Chinese Center for Disease Control and Prevention, the unmasked man infected 33 unmasked park visitors and two unmasked park workers with the coronavirus omicron subvariant BA.2.76 during his short run. The agency claimed transmission occurred in fleeting outdoor encounters as he trotted past people on a four-meter-wide foot path. Many others were infected without any close encounter. Twenty of the 33 infected park goers became infected by simply visiting outdoor areas of the park the jogger had previously passed through, including an entrance gate. The two infected workers, meanwhile, quickly passed the infection on to four other colleagues, bringing the jogger's park outbreak total to 39.

To support these unusual conclusions, the CCDC cited case interviews, park surveillance footage, and SARS-CoV-2 genetic data, which reportedly linked the cases but is notably absent from the report.

Enlarge / Parents work on their computers while their son entertains himself at their home in Boston in April 2020. (credit: Getty | Boston Globe )

Respiratory illnesses are raging this fall, slamming children particularly hard. Cases of influenza-like illnesses are off to a startlingly strong and early start this season. RSV—respiratory syncytial (sin-SISH-uhl) virus—continues to skyrocket. A stew of SARS-CoV-2 variants is still simmering in the background. And the rabble of usual cold-season viruses, such as rhinoviruses and enteroviruses, is also making the rounds.

RSV national trends. (credit: CDC )

With the surge in infections, children's hospitals around the country have reported being at capacity or overwhelmed, as Ars has reported before. But another effect of the crush of viruses is a squeeze on the workforce. As The Washington Post first reported Tuesday , the US broke its record last month for people missing work due to childcare problems—such as having children home sick and childcare facilities or schools shuttered due to staffing shortages and sickness.

Outpatient respiratory illness visits. (credit: CDC )

In October, more than 100,000 employed Americans missed work for childcare-related problems, according to data from the US Bureau of Labor Statistics . That is more missing workers than in any other month in recent records, including the entirety of the COVID-19 pandemic, during which many childcare facilities and schools closed down for extended periods. At the height of pandemic-related shutdowns in 2020, the number of Americans missing work for childcare problems only reached the low 90,000s.

Enlarge (credit: Getty | Future Publishing )

The new bivalent COVID-19 booster spurred neutralizing antibody levels that were fourfold higher against the omicron subvariants BA.4/BA.5 in older adults than those seen after the original booster, Pfizer reported Friday .

The new data may help calm concerns about whether the updated booster is an improvement over the previous booster. But the fall booster campaign—aimed at preventing another devastating winter wave—still faces considerable challenges. For one thing, a shockingly low number of Americans are rolling up their sleeves to get the shot.

Better boost

Experts all agree that the new booster shot, like the old one, will revive waning immune responses to SARS-CoV-2 and provide strong protection from severe COVID-19. But some experts have expressed skepticism about whether the updated bivalent booster—which in part targets omicron subvariants BA.4/BA.5—will offer a clinically meaningful advantage over the previous booster in preventing mild infections against the subvariant.