San Francisco: As the mysterious pneumonia cases in children rise across the world, Massachusetts has become the second US state to report a sudden surge in the number of pneumonia cases in young kids. Ohio was the first US state that recorded 142 cases of pneumonia in children since August -- above the county average -- 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, reports the New York Post. However, physicians in western Massachusetts believe it is mostly RSV, a respiratory virus that kills more than 10,000 Americans each year. "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. "RSV can cause lower viral respiratory infections, so they get spread to your lungs," the doctor added. The illness has spread across multiple school districts and the average age of those fallen ill is 8. Also ReadSpotify announces to cut 17 per cent of jobs, third round of layoffs this year The US outbreaks come as pneumonia cases in children are unexpectedly surging in the Netherlands at an alarming rate. Last week, the US Centers for Disease Control and Prevention (CDC) said that the recent pneumonia outbreak in China among young children is not caused by any new virus. CDC Director Mandy Cohen said it is related to existing pathogens like Covid, flu, RSV and mycoplasma. "We believe there is no new or novel pathogen," Cohen said during a House Energy and Commerce Subcommittee on Oversight and Investigations hearing. "These are related to existing pathogens -- Covid, flu, RSV and mycoplasma, a bacterium that can infect the lungs." The most common symptoms include cough, fever and fatigue. Among the pathogens recovered included Mycoplasma pneumoniae, Streptococcus pnuemoniae and Adenovirus. The health authorities called for taking necessary precautions such as washing hands, and staying home when ill. Separately, the Netherlands and Denmark have also reported cases.