Massachusetts has become the second US state to report a large uptick in the number of child pneumonia cases amid a mysterious viral outbreak in China.

Doctors in the Bay State noticed the rise in cases as Ohio reported enough cases to meet that state’s definition of an outbreak.

But physicians in western Massachusetts believe it is mostly RSV, a respiratory virus that kills more than 10,000 Americans each year — mostly young children and the elderly.

“This is the season for RSV and we’re seeing a whole lot of it … a lot of kids with upper viral respiratory infections, cough, runny nose, some fevers,” Dr. John Kelly from Redwood Pediatrics in East Longmeadow told Western Mass News.

“And the thinking with RSV is that it can cause lower viral respiratory infections, so they get spread to your lungs.”

He said most patients get better within a few days, but warned, “There are no medications to give to cure [it].

“Once you have it, [it] is all supportive care.”

In Ohio, the Warren County Health District recorded 142 cases of pneumonia in children since August — above the county average.

However, officials do not think it is a new respiratory disease, but “rather a large uptick in the number of pneumonia cases normally seen at one time,” according to a press release.

The illness has spread across multiple school districts and the average age of those fallen ill is 8, the local health district said.

“The information was shared so that individuals would be aware of illness in the community and take necessary steps to protect their health,” the health district said.

“It is not uncommon for respiratory illnesses to spread in the community during this time of year.”

Federal officials also said they do not currently believe there is a link between the pneumonia cases across the United States and the mysterious illness affecting China.

“We are seeing about the same number and type of pneumonia cases in children and adults as we typically see this time of the year,” David Daigle, a spokesman for the Centers for Disease Control, said in a statement to the Post.

“We will continue to closely monitor pneumonia infections and other respiratory infections and work with local health officials to ensure communities have the tools they need to respond,” he noted.

The US outbreaks come as pneumonia cases in children are unexpectedly surging in the Netherlands at an alarming rate.

Last week, 80 out of every 100,000 children in the Netherlands between ages 5 and 15 were treated for pneumonia, reported the Netherlands Institute for Health Services Research.

Pneumonia cases among tots ages 4 and under were also on the rise, jumping from 124 to 145 per 100,000.

This is the biggest pneumonia outbreak the Utrecht-based research institute has recorded in recent years.

For comparison, at the height of the flu season in 2022, there were 60 recorded cases of every 100,000 children ages 5 to 15.

But it remains unclear if any of these outbreaks are related to a mysterious child pneumonia outbreak in China, where hospitals are becoming crowded and have long wait times, with a return of masking and protective suits.

Some schools in Beijing have also suspended classes that saw high infection rates, according to the Wall Street Journal.

The World Health Organization has issued an official information request, which seeks “additional epidemiologic and clinical information, as well as laboratory results” from China, WSJ reports.

The request itself is routine, but WSJ said it’s “relatively rare” for the United Nations agency to do so publicly.