A new omicron subvariant named JN.1 has rapidly risen to become the dominant strain of COVID-19 in the United States. This highly mutated variant accounted for over 60% of new coronavirus infections nationwide in late December.
JN.1’s meteoric rise has sparked concern due to its increased immune evasion abilities compared to other prevailing strains. However, it is still unclear whether this new variant will cause a major surge in cases this winter.
Here is everything we know so far about the fast-spreading JN.1 subvariant:
Where Did JN.1 Come From?
JN.1 descends directly from another omicron offshoot called BA.2.86. This parental strain, nicknamed “Pirola,” first emerged last summer but did not gain much traction in the U.S. or globally.
Pirola itself descended from omicron’s BA.2 sublineage, making it part of the same omicron family as variants like BA.5 and BF.7. However, JN.1 split off and acquired concerning mutations that appear to give it a competitive edge.
Specifically, JN.1 possesses a mutation called L455S in the receptor binding domain of its spike protein. This alteration likely enhances the virus’s ability to escape antibodies generated by vaccination and prior infection.
JN.1 was first detected in the United States in September 2022. By November, it accounted for less than 1% of COVID cases nationally. Just a few weeks later, it had surged to make up over 20% of sequenced infections.
How Fast Is JN.1 Spreading in the U.S.?
In a very short period, JN.1 overtook its parental variant BA.2.86 and became the fastest-spreading subtype in the country.
According to Centers for Disease Control and Prevention (CDC) data, JN.1 caused around 21% of U.S. COVID cases in early December. By late December, it comprised a staggering 60% of new infections sequenced.
The CDC warned that JN.1’s rapid national growth indicates it is likely more transmissible and better at evading immunity than other prominent strains.
JN.1 has also been identified in at least 41 other countries so far. On December 18th, the World Health Organization designated it as a global “variant under monitoring” due to its expanding reach.
Which Variant Did JN.1 Replace?
Before JN.1 arrived on the scene, the dominant COVID variant in the U.S. was BQ.1.1 and its close relative XBB.1.5. This variant and its offshoots drove a mild surge in cases during the fall and early winter months.
XBB.1.5 itself only gained prominence in October after overtaking BA.5, which had been the predominant strain for most of the summer.
All of these recent dominant variants descend from the original omicron strain that fueled record-high case counts in late 2021 and early 2022.
JN.1 managed to outcompete its close cousins XBB and BQ.1.1 due to crucial differences in mutations. It seems especially adept at dodging the immunity people have accumulated through vaccination and previous bouts of COVID.
What Symptoms Does JN.1 Cause?
Currently, there is no evidence that JN.1 causes different or more severe symptoms compared to other omicron subvariants.
According to the CDC, the types of symptoms people experience typically have more to do with their immunity and underlying health than the particular variant they caught.
Early data indicates the symptoms of JN.1 mirror those of earlier omicron offshoots. Common symptoms include:
- Sore throat
- Runny nose
- Cough
- Congestion
- Fever or chills
- Fatigue
- Headache
- Muscle/body aches
- Loss of taste or smell
- Shortness of breath
Some anecdotal reports from doctors suggest respiratory symptoms may start with a sore throat before progressing to nasal congestion and cough. This differs slightly from original omicron, which generally began with nasal symptoms.
Despite mutations that help JN.1 dodge antibodies, real-world data has not demonstrated that it causes more severe disease or hospitalization than other variants at this time. Its mutations do not seem to affect the chest-level lungs as much as the upper respiratory tract.
However, experts caution it is still very early, and the CDC notes it can take weeks or months to characterize a variant’s clinical severity. People with risk factors like old age and chronic illnesses remain most vulnerable to critical illness.
Will JN.1 Cause a Surge This Winter?
The rapid rise of JN.1 comes as COVID-19 hospitalizations and test positivity have been increasing nationwide in recent weeks.
Whether JN.1 alone will trigger a major viral surge remains unclear. Some experts believe rising hospitalizations and deaths will be driven by a “tripledemic” of JN.1, influenza, and RSV rather than just one virus.
In the coming weeks, JN.1 cases are expected to continue rising and peaking around the new year, mirroring the seasonal ebb and flow of the past two COVID winters.
However, experts cannot predict exactly how big this potential JN.1 wave will be. Encouragingly, ICU admissions and deaths have not risen proportionally to cases so far. Widespread immunity offers some protection against severe outcomes.
JN.1’s rapid mutations do appear to give it increased transmission potential compared to its omicron cousins. Whether faster spread also translates into an infection spike will become evident as more data emerges.
Do Vaccines Work Against JN.1?
Fortunately, lab studies indicate our current COVID vaccines still provide protection against JN.1, even if immunity may be reduced compared to earlier variants.
The recently updated bivalent booster shots are designed to generate antibodies against the omicron BA.4 and BA.5 subvariants. JN.1 is descended from a different branch of the omicron family tree.
However, getting the new booster still offers improved protection by further broadening and strengthening immune defenses. Vaccines help prevent severe disease requiring hospitalization, even for radically mutated variants.
Experts unanimously urge all Americans age 6 months and older to get the updated COVID booster for optimal protection this winter. Adolescents can also receive the original Pfizer primary vaccine series if unvaccinated.
However, booster uptake remains low, with less than 20% of adults receiving the newest shot. Widespread vaccination is critical for limiting viral spread and preventing strain on healthcare systems.
Can We Treat JN.1 Infections?
The CDC states that current COVID treatments are expected to work just as well against JN.1 as other circulating variants.
Oral antiviral pills like Paxlovid and monoclonal antibody infusions remain potent options for treating high-risk patients within the first days of infection. These therapies can lower the chances of hospitalization and death.
Lab tests show JN.1 remains vulnerable to these authorized treatment options. Real-world data will reveal more about its potential resistance over time.
The key is starting antiviral pills quickly, as they work best within 3-5 days of the onset of symptoms. People with COVID risk factors should seek early treatment from a healthcare provider.
Does JN.1 Escape Detection by Tests?
There is no evidence that JN.1 goes undetected by standard COVID diagnostic tests. Both PCR and rapid antigen tests successfully identify this new variant.
Some mutations in other variants have occasionally reduced test sensitivity. However, experts say all commercially available tests can identify JN.1 just as well as previous strains.
Continued screening through testing remains imperative, especially heading into the holiday season. People with any respiratory symptoms or exposures should test immediately and isolate if positive.
Rapid at-home tests are an easy way to check infection status before gatherings or travel. PCR tests offer the highest sensitivity for those with symptoms or negative rapid results.
How Can We Protect Ourselves Against JN.1?
The same common-sense precautions that prevent COVID spread will also protect against transmitting or acquiring the JN.1 variant:
- Get all recommended COVID vaccine doses and flu shot
- Improve indoor ventilation
- Wash hands frequently
- Wear high-quality masks in crowded public settings
- Test before gatherings or if symptomatic
- Stay home when sick
- Treat quickly if high-risk and infected
While JN.1 demonstrates some ability to evade immunity, experts say our vaccines still substantially reduce risks of severe illness. Plus, masking and improved ventilation make indoor spaces safer.
Staying vigilant with preventative measures remains key as JN.1 cases climb across the country in the weeks ahead. Protecting vulnerable groups continues to be the top priority.
What Comes Next?
Experts will carefully analyze rates of JN.1 infections, hospitalizations and deaths in different regions to understand its impact as the variant becomes dominant nationwide.
CDC will monitor clues about JN.1’s real-world virulence and ability to reinfect people. Genetic sequencing will also provide information about whether it develops any new concerning mutations.
It typically takes at least a couple months for the implications of a novel variant to become fully clear. For now, increased caution and prevention measures can help individuals stay safe.
JN.1’s rapid rise to prominence exemplifies how unpredictable and changeable the COVID landscape remains. With this virus, the situation can shift quickly, especially as immunity wanes.
Vigilance, adaptation and access to the latest vaccines and treatments will remain crucial tools for addressing future variants that may emerge after JN.1.
