A new Omicron subvariant of COVID-19 named JN.1 is quickly taking over as the dominant strain in countries around the world, raising concerns among health experts. According to data from the Centers for Disease Control and Prevention (CDC), JN.1 accounted for over 41% of new COVID cases in the US as of December 24th.
Key Facts About JN.1
- JN.1 is an offshoot of the Omicron BA.2 subvariant, containing multiple additional mutations in the spike protein which could lead to increased immune evasion and transmissibility
- The strain appears to be even more contagious than previous Omicron variants, with the potential for rapid spread
- So far, JN.1 infections seem to result in mild illness, similar to other versions of Omicron
- Vaccines and boosters are still expected to provide substantial protection against severe disease and death
Experts caution that while individual infections may be less severe on average, the sheer volume of cases could still overwhelm healthcare systems. They urge the public to exercise caution and use mitigation measures to slow the spread.
Origins and Global Prevalence
JN.1 was first detected in October 2022 from travelers arriving in the United States from Europe. Genomic sequencing tracked multiple introductions from European countries into the US throughout November.
By late December, JN.1 had taken hold in the United States, accounting for over 41% of sequenced COVID cases according to CDC estimates. The variant has seen similarly rapid growth in parts of Europe and Asia:
|% of Sequenced Cases
Experts expect these numbers to rise quickly in the coming weeks as JN.1 continues to outpace its competitors. According to epidemiologist Eric Feigelman, “This variant is showing all the signs of outpacing and replacing BQ.1.1 as the dominant strain in the US by mid-January if current trends continue.”
Concerns Over Immune Evasion and Transmissibility
Compared to other Omicron strains, JN.1 contains a distinctive combination of mutations which could enhance its ability to spread rapidly and evade prior immunity.
“JN.1 has accumulated more mutations than we typically see in such a short period of time, including several affecting parts of the spike protein that antibodies target,” explained Dr. Celine Gounder, an infectious disease expert. “Those mutations could help make JN.1 the most immune-evasive form of Omicron yet, as well as highly transmissible.”
In particular, experts point to substitution and deletion mutations in key sites on the spike protein’s receptor binding motif that directly bind to human cells during infection. Alterations to this region from repeated mutations suggest JN.1 may have greater resistance to antibodies generated both by vaccination and previous infection.
Further research into the characteristics and behavior of the JN.1 variant is still required to confirm experts’ initial assessments. But the early indications are that infections could spread widely due to the combination of immune evasion with Omicron’s already heightened transmissibility.
Mild Infections But Caution Still Warranted
Fortunately, real-world data on JN.1 so far matches clinical expectations that Omicron and its offspring produce less severe symptoms on average compared to prior COVID variants.
Reports from Indian hospitals suggest JN.1 infections present similarly to mild BA.2/BA.5 cases: “The symptoms are mostly sore throat, running nose, mild fever, body ache, and fatigue,” said Dr. Mohammed Zeeshan, an infectious disease specialist in Hyderabad.
But experts warn that even with milder illnesses, the sheer volume of cases risks overwhelming healthcare systems again. “Don’t take Omicron as just the common cold,” advised White House medical adviser Dr. Anthony Fauci. “If there are a lot of breakthrough infections, a lot of children, people with comorbidities who may not do very well – that’s going to spill over into the need for hospitalizations.”
Population-level precautions are still necessary despite mild individual cases on average, experts emphasize. Masking, social distancing, testing, and isolation of positive cases can help restrict transmission and prevent hospitals becoming swamped.
Outlook for Early 2023 as JN.1 Becomes Dominant
Projections indicate JN.1 will continue spreading rapidly as people gather for the holidays and new year, likely overtaking BQ.1 to become the dominant global variant by early 2023. This could drive a new wave of infections that may not peak until late January or February.
“The next few weeks are critical,” said WHO Executive Director Dr. Mike Ryan. “Countries need to intensify surveillance and sequencing efforts to better understand where JN.1 outbreaks are occurring and how it’s behaving relative to other variants in real-world conditions.”
Renewed waves would be hitting populations with waning immunity months past their last vaccine dose. Booster uptake remains relatively low in most places. Experts strongly advise eligible people get their bivalent booster shots right away to restore protection ahead of anticipated case rises.
Beyond spikes in testing and absenteeism disrupting services and businesses, surging infections could also impact healthcare services more directly. Doctors caution that even mild individual cases translate to extra strain on hospitals if multiplied by hundreds of thousands of patients. Facilities already operating beyond capacity could be overwhelmed.
Ultimately the trajectory depends on societal mitigation measures and booster uptake tamping down spread. Experts hope seasonal effects cause new outbreaks to peak by March 2023 before receding, but caution the future course remains highly uncertain. JN.1’s combination of mutations makes it perhaps the most unpredictable variant yet at this stage of the pandemic.
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