Ohio announced an outbreak of pneumonia. Similar outbreaks are happening in China and Europe.

• Ohio public health officials announced an outbreak of pneumonia in children on Wednesday.
• Experts say the Ohio outbreak is unrelated to pneumonia outbreaks in China and Europe.

Cases of pneumonia in children are increasing in Ohio, leading public health officials to declare an outbreak.

The Warren County Health District in Ohio released statements on November 29 and November 30 stating that they have been experiencing "an extremely high number of pediatric pneumonia cases being reported this fall season." Since August, there have been a total of 145 cases. No deaths have been reported.

The announcement comes after hospitals in China started reporting increasing clusters of pneumonia in children in mid-October. Denmark and the Netherlands have also reported increasing cases of pneumonia.

Health officials in Ohio said that there is "zero evidence" that the Ohio outbreak is connected to other outbreaks of respiratory illness nationally or internationally.

The increase in pneumonia is likely from common causes

Pneumonia is a lung infection that can cause symptoms like fever, cough, or shortness of breath.

Public health experts in Ohio believe that the surge is not due to a new virus; but it's an uptick of the number of normal pneumonia cases seen at this time of year.

Officials have tested some of the children with pneumonia, and have found several bacteria that can cause illness, including Streptococcus pneumoniae — the most common bacterial cause of pneumonia — as well as Mycoplasma pneumoniae, and Adenovirus.

Experts say there's no reason to panic

Although multiple areas around the globe are experiencing pneumonia outbreaks, experts don't believe the cases are cause concern yet.

In China, the surge in cases is likely due to the lifting of COVID-19 restrictions last December and a resulting "immunity gap," according to the World Health Organization. Children who were in lockdowns for the past several years may just be getting exposed to some respiratory pathogens for the first time.

And in Ohio, officials say the number of cases is still aligned with seasonal trends.

"Based on our provisional assessment, we are seeing seasonal trends," a spokesperson from the Centers for Disease Control and Prevention told ABC News. "Nothing is appearing out of the ordinary, but we are continuing to monitor."

While there have been some hospitalizations in Ohio, the "vast majority" of children are recovering and returning to school, Dr. Clint Koenig, the medical director of Warren County Health District, told ABC News.