(NewsNation) — A spike in respiratory infections in children in China has caused alarm around the globe, but the Centers for Disease Control and Prevention says there is no cause for concern.

China told the World Health Organization the spike is being caused by known viruses like the flu, COVID-19 and RSV and is not the result of a new pathogen.

CDC Director Mandy Cohen testified on Capital Hill that the agency has no reason to believe there is an unknown virus circulating.

“We do not believe this is a new or novel pathogen, we believe this is all existing, meaning COVID, flu, RSV, mycoplasma,” she said. “Chinese officials have shared with us that there is no novel pathogen. We were able to corroborate that information with other sources from our European Union partners and others to make sure we are getting the complete picture.”

But Republican lawmakers are pushing back on that, with Sen. Marco Rubio and others saying, in part “we should not wait for the WHO to take action.” The letter went on to say the U.S. must take necessary steps to protect the health of Americans and the economy, including restricting travel between the U.S. and China until more is known about the new illness.

The WHO did emphasize these are not new pathogens, but the photographs of long lines and people with masks are reminding people of the early days of 2020. There are also headlines out of Massachusetts and Ohio where a number of children are getting diagnosed with pneumonia.

NewsNation spoke to Dr. Amesh Adalja, an infectious disease expert, about what’s going on. He said China’s extended lockdown might be to blame.

“I think this is just what happens when you have people who are social distanced for a certain period of time, when they start to interact all those common pathogens come back and they come back with a vengeance,” he said.

Adalja noted the U.S. also saw a spike in RSV, especially among children, in 2022 when things really started opening up.