Concerned about the U.S. "Quad Pandemic"...Flu, COVID-19, RSV, and Noro spread simultaneously.

With the Arctic cold wave predicted across the United States, various infectious diseases such as flu, COVID-19, respiratory syncytial virus (RSV), and norovirus are on the rise, according to CNN and AP.

CNN and others cited data from the U.S. Centers for Disease Control and Prevention and the CDC, saying that at least 5.3 million flu cases were reported across the U.S. this winter, 63,000 of whom were hospitalized.

The death toll from the flu has reached 2,700, including 11 children.

In particular, as the number of patients surged around the end of the year holiday season, the level of disease epidemic was rated "high or very high" in 40 U.S. states last week, the Associated Press reported.

He also added that not a few patients have been infected with COVID-19, which causes flu-like symptoms, and RSV, which is particularly dangerous for infants and the elderly.

Fortune magazine, a U.S. business magazine, analyzed that there is a concern about a quad pandemic in which four infectious diseases spread at the same time as the flu, COVID-19, and RSV spread to norovirus.

Norovirus, an uninvited winter visitor that can cause symptoms such as vomiting, diarrhea, chills and fever, is also spreading faster than usual, with 91 cases reported early last month, the CDC said.