A new COVID-19 variant named JN1 is rapidly spreading across the United States, causing a record surge in cases that is overwhelming hospitals in some regions. First detected in late 2022, JN1 has quickly become the dominant strain, raising alarms about its increased transmissibility and ability to evade immunity.
JN1 Now Accounts for Over 75% of US COVID Cases
According to data from the CDC, JN1 now makes up over 75% of sequenced COVID-19 cases across the US as of early January 2024. The variant overtook Omicron as the predominant strain just weeks after it was first detected in the country.
Experts say JN1 is the most transmissible form of COVID-19 to date, spreading at a pace not seen since the earliest days of the pandemic. Its rapid rise indicates it is considerably more contagious even than Omicron, which itself outpaced Delta and other earlier variants.
“This is certainly the steepest, most vertical rise we’ve seen since the very first COVID virus appeared,” said Dr. Eric Topol, founder and director of the Scripps Research Translational Institute.
The sudden spike in cases from JN1 is overwhelming hospitals and healthcare workers in some regions, recalling the darkest days of previous COVID surges.
Concerns Over JN1’s Ability to Evade Immunity
One of the most worrying aspects of JN1 is its apparent ability to partly evade existing immunity from vaccination and prior infection. Early lab studies indicate it is equipped with new mutations that enable the virus to escape neutralizing antibodies.
“The mutations we see in the JN1 variant are located in regions of the spike protein that antibodies target,” explained Ravindra Gupta, professor of clinical microbiology at the University of Cambridge. “This allows the virus to slip past immune defenses and continue infecting cells.”
This immune evasion raises the risk of reinfection even in those who were previously infected by other Omicron subvariants. It also reduces the protective benefit of vaccination, though boosters still appear to provide substantial defense against severe disease and death.
More study is still needed to fully gauge JN1’s ability to circumvent immunity relative to prior variants. But current evidence shows it at least partly escapes neutralization, fueling its rapid spread.
Surge Impacting Both Unvaccinated and Vaccinated
The JN1-driven surge is impacting both unvaccinated and vaccinated individuals across age groups. Its immune evasion enables more repeat infections in those with prior immunity.
“We are seeing a striking increase in reinfections from JN1, even just months after a previous Omicron infection,” saidisode,” said Jennifer Nuzzo, epidemiologist at the Johns Hopkins Bloomberg School of Public Health.
Experts say vaccines continue providing protection from hospitalization and death, especially for those who got the updated bivalent booster. But their benefit is dampened against infection due to JN1’s mutations enabling immune evasion.
“While vaccines remain critically important, we unfortunately can expect more breakthrough cases with JN1 even among the boosted,” Nuzzo said.
JN1 Causing More Severe Illness for Some
While the severity of JN1 infections is being closely analyzed, early evidence suggests it may cause more severe illness compared to Omicron and its BA.5 subvariant. Some regions are reporting an uptick in hospitalizations and need for intensive care from the JN1 wave.
“We are certainly seeing a real increase in ICU admissions in my hospital network,” said Dr. Megan Ranney, physician and academic dean at Brown University’s School of Public Health. “And anecdotally, the patients skewing more severe tend to be those infected with JN1 compared to other virus strains.”
There are also indications children and infants are experiencing more intense upper respiratory symptoms from JN1 such as croup and bronchitis. While still typically mild, these illnesses are landing more young kids in emergency rooms and pediatric hospital wards.
“Parents should be on the lookout for difficulty breathing, high fever lasting over 24 hours, or signs of dehydration,” advised Dr. Allison Messina, chief of infectious diseases at Johns Hopkins Children’s Center. “These are red flags to seek medical attention.”
New and Different Symptoms Reported
In addition to its increased transmissibility and immune evasion, JN1 presents somewhat different symptoms compared to earlier COVID variants. Patients are reporting combinations of fever, sore throat, runny nose, headache, fatigue and gastrointestinal upset.
“I’ve seen more nausea, vomiting and diarrhea with JN1 cases,” said Dr. Sabrina Assoumou, infectious disease physician at Boston Medical Center. “Whereas earlier variants were more straight respiratory.”
Loss of taste and smell also seems less predominant with JN1 compared to ancestral COVID strains and the original Omicron variant. But more analysis is still needed to confirm the precise symptom patterns associated with the newest variant.
Table: Key Differences Between COVID Variants
|Fever, cough, fatigue, loss of taste/smell
|Fever, cough, fatigue, loss of taste/smell
|Fever, cough, headache, sore throat
|Runny nose, congestion, headache, fatigue
|Sore throat, runny nose, nausea/vomiting, diarrhea
This table summarizes the key traits of major COVID variants to highlight how JN1 differs from those that came before it. JN1 combines extremely high transmissibility and considerable ability to evade existing immunity with atypical symptoms that mimic other respiratory viruses.
Public Health Mitigation Measures Still Key Against JN1
As JN1 continues its swift spread, public health leaders emphasize basic mitigation measures remain vital to control transmission: indoor masking, improved ventilation, testing, staying home when sick, and vaccination.
“Masks, filters, distancing – these simple tools make a real dent we urgently need with this wave hitting so fast and hard,” said former Baltimore Health Commissioner Leana Wen. “And please, get boosted if you are eligible – vaccines are not obsolete with JN1 even if they are compromised.”
Officials also advise getting tested soon after symptom onset, as JN1 appears have a shorter incubation period compared to prior variants. Identifying infections earlier aids isolation and contact tracing efforts to slow the spread.
There are also calls for more funding to accelerate the development of variant-specific vaccines and therapeutics tailored to strains like JN1 with extensive mutations enabling immune escape. Having tools matched to emerging variants could prove critical if COVID continues mutating rapidly.
What Comes After the JN1 Wave Peak?
Some models forecast the JN1 wave could peak by early February 2024 in regions hit earliest like the Northeast. But public health experts warn that plateau may be followed by resurgent waves, just as previous COVID surges rebounded after receding.
“I fear we could see a peak falsely signal the worst is behind us before other sublineages of JN1 or even new variants emerge to fuel fresh spikes,” said Eric Feigl-Ding, epidemiologist and Senior Fellow at the Federation of American Scientists. “This virus has shown its ability to keep mutating to find ways to thrive.”
The recent holiday gathering season likely accelerated JN1’s exponential growth while also driving up flu and RSV cases still circulating at high levels post-peak. The combined impact across three major respiratory viruses will continue straining healthcare systems even after COVID hospitalizations start declining.
“Our hospitals simply do not have the capacity to handle such an unrelenting onslaught of respiratory illness,” said UCLA’s Anne Rimoin, professor of epidemiology. “We will be dealing with the fallout from this triple viral threat for some time.”
Only time will tell whether JN1 represents COVID’s last major gasp or if more dangerous variants lie ahead in the virus’s continual evolution. But with its unmatched transmissibility and immune escape, the new strain has demonstrated the pandemic is far from controlled even after three long years. JN1 has made clear that SARS-CoV-2 still has plenty of tricks up its sleeve we have yet to reckon with.
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