LOS ANGELES - The United States has seen an uptick in flu and COVID-19 cases amid holidays, and health experts are concerned about the increasing health risks brought by the simultaneous spread of respiratory illnesses.

The amount of respiratory illnesses causing people to seek healthcare is elevated or increasing across most areas of the country, according to the US Centers for Disease Control and Prevention (CDC).

This rise is attributed to several factors, including holiday gatherings, a high number of unvaccinated individuals, and the emergence of a new, potentially more transmissible variant of the coronavirus, according to health experts.

Seasonal influenza activity is elevated in the United States, and continues to increase in most parts of the country, the latest CDC data showed.

There have been at least 5.3 million illnesses, 54,000 hospitalizations, and 3,200 deaths from flu in the United States so far this season, according to CDC estimates.

The number of weekly flu hospital admissions continues to increase, with over 9,800 patients admitted to hospitals with flu in the week ending Dec 16, according to the CDC.

A total of 14 flu-associated pediatric deaths have been reported in the country this season.

Nationally, laboratory test positivity for flu and emergency department visits due to flu are increasing, according to the CDC.

Meanwhile, a new coronavirus subvariant JN.1 is spreading fast in the United States, becoming a significant contributor to new COVID-19 cases in the country.

JN.1 is currently the fastest growing variant and the dominant one in the United States, and is responsible for over 44 percent of new infections across the country, up from the previously reported 21.4 percent, according to the CDC.

The CDC estimated that JN.1 is strongest in the Northeast regions including New Jersey and New York, where it accounts for nearly 57 percent of cases.

JN.1, which is closely related to the variant BA.2.86 that the CDC has been tracking since August, was first detected in the United States in September 2023.

JN.1 is likely more transmissible than other variants "or better at evading our immune systems than other circulating variants", said the CDC.

Health experts are concerned that the simultaneous spread of respiratory illnesses may heighten the risk for widespread impact on public health and healthcare systems, urging the public to take preventive measures, including vaccination and adhering to health guidelines, to mitigate the spread of infections and avoid severe outcomes of the viruses.