Covid-19 variant JN.1 is now the leading cause of infections in the US. Here’s what you need to know

December 22, 2023

Originally Published: 22 DEC 23 11:16 ET

Updated: 22 DEC 23 13:00 ET

By Amanda Musa, CNN

(CNN) — The Omicron coronavirus subvariant JN.1 now makes up 44.2% of Covid-19 cases in the United States, according to the US Centers for Disease Control and Prevention.

As of Friday, CDC data estimates indicate that the quickly spreading variant is now causing almost half of infections nationwide, when just days ago it was estimated that JN.1 caused only around 20% of infections.

JN.1 makes up nearly 57% of new Covid-19 cases in the Northeast, according to the new CDC data. Earlier this week, the variant was already dominant in the region – causing about a third of new infections at the time.

Globally, JN.1 continues to be reported in multiple countries, and its prevalence has been rapidly increasing. Earlier this week, the World Health Organization classified JN.1 as a “variant of interest” and evaluated the public health risk posed by JN.1 to currently be low at the global level.

The CDC estimates that prevalence of JN.1 more than doubled in the US between late November and mid-December. It seems to be getting an assist from holiday travel and waning immunity.

Variant trackers say they expect JN.1 to become the leading coronavirus variant around the world in a matter of weeks.

Vaccine immunity is expected to remain “cross-reactive” to JN.1 – a descendent of the variant BA.2.86, a subvariant that came to the world’s attention over the summer because of the large number of changes to its spike proteins.

The World Health Organization named it a variant of interest on Tuesday because of its “rapidly increasing spread” but noted that the additional public health risk remains low.

Covid-19 caused 7 hospitalizations for every 100,000 people in the week ending December 9, accounting for a 3% increase, CDC data shows.

More than three-quarters of US hospital beds are currently in use due to Covid-19 hospitalizations, which is largely in line with trends over the past three years. However, the CDC warns that rising respiratory virus hospitalizations could strain health care resources in the coming weeks.

Overall Covid-19 data shows weekly hospitalizations have been trending down in recent weeks.

Meanwhile, flu hospitalizations are rising but remain steady compared with recent weeks, according to CDC data. Flu-like activity is very high in five states and high in 15 states.