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NYC Issues Plea as ‘Most Transmissible Form of COVID-19 We Know of to Date’ Spreads


  • You’ve probably heard about the XBB.1.5 variant; it’s the latest “most transmissible COVID variant yet” and appears to be better at binding to human cells, which may make it more adept at infecting
  • There’s no evidence at this point that the strain, a combination of two prior omicron subvariants, is more lethal or more likely to cause COVID complications, but NYC health officials say XBB.1.5 may be more likely than other variants to infect vaccinated people and people who already had COVID
  • Nowhere is XBB.1.5 more prevalent than in the northeastern United States, according to the CDC — and rolling hospitalization and death rates, along with cases, are climbing accordingly

The unprecedented infectiousness of XBB.1.5 prompted renewed calls for public caution Friday from New York City health officials, who announced the latest omicron descendant, widely believed to be behind the latest case wave, now accounts for nearly three-quarters of all coronavirus circulating across the five boroughs.

Calling the new strain “the most transmissible COVID variant we know of to date,” the city’s health department said XBB.1.5 is now responsible for 73% of all COVID cases sequenced in New York City. Omicron, and its litany of descendants including XBB.1.5, is the only variant of concern still currently in circulation, public health officials say.

Health data, though, only reflects sequenced cases through the first of the year, and a relatively small share of positive cases undergo the exhaustive process required to isolate variants (just 3% in the city’s latest week of available data and trending downward). That means XBB.1.5’s actual prevalence is likely considerably higher than reported.

According to CDC variant data updated Friday, XBB.1.5 accounts for an estimated 82.7% of COVID circulating in the New York region, which also includes New Jersey, the Virgin Islands and Puerto Rico, and could represent as many as 88.2% of cases. That’s up from a 72.7% baseline estimate and 81.2% high in last week’s report.

Omicron subvariant XBB.1.5 now accounts for 73% of all sequenced COVID-19 cases in NYC. XBB.1.5 is the most transmissible form of COVID-19 that we know of to date and may be more likely to infect people who have been vaccinated or already had COVID-19.

— nychealthy (@nycHealthy) January 13, 2023

City health officials also noted that XBB.1.5 may be more likely to infect people who have been vaccinated or already had COVID — a reality that Dr. Ashish Jha, head of the White House COVID Task Force, acknowledged last week.

As Jha put it, if you haven’t had COVID since July or were last vaccinated prior to the bivalent update in September, “Your protection against an XBB.1.5. infection is not that great.”

Reinfection data from the state underscores the point. The 11.7 per 100,000 reinfection rate for New York City in the prior week is on par with the reinfection numbers seen during the initial omicron wave downswing in January 2022. The numbers are starkest on Long Island, with has a 15.8 per 100,000 reinfection rate, mirroring mid-January 2022.

New York state breakthrough data is incomplete and not broken out regionally, but does reflect an increase in breakthrough cases through December, which could reflect the actual emergence of XBB.1.5, given we know variants are often circulating well before detection. While the breakthrough case numbers notched their first week of decline in a month in the state’s latest report, the breakthrough hospitalization rate increased, reflecting the lagging factor.

CDC covid variant data


Here are the numbers for the CDC’s New York region.

Data from the New York City health department, which varies slightly from the state’s due to reporting and other factors, fits with the apparent trend. The rolling case average overall hit a recent spike in December, but COVID hospitalizations and deaths notched more recent highs (see the latest NYC trends from city health department here).

Manhattan appears to be struggling the most on the COVID front right now, CDC data shows. Over the last week, it says the borough’s weekly case rate is up 13.41%, its weekly death rate is up 37.93% and its test rate is up 14.54%.

By comparison, the death rate in Queens is down 5.36% and cases are up just 2.87%. Testing in the borough is up 8.93%. Brooklyn also is seeing a downward trend in weekly death rates (down 3.23%) as well as in cases (down 1.17%) while testing is up 7.03%. The Bronx is seeing its weekly case rate rise (up 4.81%) but its death rate drop (by 2.94%) – and COVID testing is up 12.19% over the last seven days on a per 100,000 basis.

Staten Island is seeing the biggest week-over-week declines in both case (down 13.69%) and death (down 11.11%) rates, according to the CDC. Its test rate is also up.

Any way you look at it, though, NYC data on those three metrics — cases, hospitalizations and deaths — pales in comparison to the heights associated with the first omicron wave, a testament, experts say, to the power of vaccination, bivalent boosting and proven mitigation efforts like mask-wearing, hand-washing and testing regularly.

Face masks remain the recommendation in New York City — city, state and federal public health agencies all agree — regardless of vaccination status when it comes to indoor settings and crowded outdoor ones given the trends.

Encouragingly, the World Health Organization said this week that omicron XBB.1.5 doesn’t appear to have any mutations known to make people sicker, but added it needs more data to draw conclusions about its severity.

The CDC said the new COVID-19 variant is responsible for 75% of new cases.