(CNN) Flu activity is increasing in the United States, the US Centers for Disease Control and Prevention reported Friday.

As of the week ending December 22, nine states are experiencing high flu activity -- Alabama, Colorado, Georgia, Kentucky, Louisiana, Maryland, New Jersey, New Mexico and South Carolina -- as well as New York City. That's an increase from the previous week, when two states, Colorado and Georgia, experienced high flu activity. Seven states and Puerto Rico are experiencing moderate flu activity. Among the four states along the southern US border, flu activity increased to high in New Mexico and moderate in Arizona, the CDC noted.

Geographically, there's widespread flu activity reported in 11 states -- Arizona, California, Connecticut, Delaware, Florida, Georgia, Massachusetts, Nebraska, New Mexico, New York and North Carolina -- and Guam.

Influenza A viruses have been dominating in the United States since the beginning of October, the CDC said, although influenza B viruses are circulating, as well.

There were four flu-related pediatric deaths reported to the CDC during the week ending December 22. There have been 11 total flu-related deaths among children in the 2018-2019 season.

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