By Aria Bendix and Jessica Herzberg — NBC News
An Ohio county is experiencing a pediatric outbreak of pneumonia, including several cases of mycoplasma or white lung pneumonia, a disease that has led to recent outbreaks among children in Denmark and China.
The Warren County Health District said Thursday that it has had an unusually high number of pediatric pneumonia cases this fall — 145 since August. The average patient is around 8 years old, depending on the district, and the most common symptoms have been cough, fever and fatigue. No deaths have been reported and illnesses are no more severe than in previous years, the district said in a news release.
Mycoplasma pneumonia cases have reached epidemic levels in Denmark and contributed to an increase in hospital admissions in China. Taiwan's Ministry of Health said on Thursday that older adults, young children and people with poor immunity should avoid travel to mainland China, Hong Kong or Macau due to the rise in respiratory illnesses there, which also include outbreaks of influenza, adenovirus and respiratory syncytial virus (RSV).
The Centers for Disease Control and Prevention (CDC) has been in communication with its counterpart in China "to make sure we understand the situation there," its director, Dr. Mandy Cohen, said Thursday at a House Energy and Commerce Committee hearing.
"We don't think this is a new or novel pathogen," he said.
The Warren County Health District in Ohio also said it did not suspect a new respiratory virus was causing the outbreak, noting that "there has been no evidence that this outbreak is related to other outbreaks, whether at the state, national or international level."
What is mycoplasma pneumonia?
Mycoplasma pneumonia is caused by bacteria that can spread through small droplets when an infected person coughs or sneezes. The bacteria can stay in the nose and throat without making a person sick, but it can cause pneumonia if it spreads to the lungs.
Mycoplasma pneumonia is usually a milder form of pneumonia, but its symptoms may last longer. Cases tend to peak every three to seven years in the United States.
"It's sometimes referred to as 'walking pneumonia,' which means you have pneumonia but you're not sick enough to be in the hospital," said Dr. James Cutrell, an associate professor of infectious diseases at UT Southwestern Medical Center in Dallas.
In older children and adults, initial mycoplasma infections often resemble chest colds and can include a sore throat, fever, headaches or a worsening cough that lasts for weeks to months, according to the CDC. Children younger than 5 often develop cold-like symptoms, such as sneezing, stuffy nose, sore throat, diarrhea, or vomiting.
Young children are more likely to have severe cases that progress to pneumonia, especially if their immune systems are weak or they have never been exposed to the bacteria before. Symptoms of pneumonia, which include cough, fatigue, shortness of breath, fever and chills, usually appear one to four weeks after someone is infected.
The World Health Organization said last week that China has reported an increase in hospitalization of children with mycoplasma pneumonia since May.
Cases in Denmark have also risen since the summer, according to the Statens Serum Institut, a Copenhagen-based research group that is part of the Danish Ministry of Health.
On Wednesday, it reported that mycoplasma pneumonia cases have increased significantly over the past five weeks. Denmark recorded 541 new cases in the week ending Nov. 26, more than triple the number recorded three weeks earlier.
Sweden, Switzerland and Singapore also recorded more than 100 cases each between April and September, according to a study published last week in The Lancet Microbe.
Why are outbreaks happening now?
Infectious disease experts said the outbreaks are cause for increased vigilance, but not panic, in the United States.
"There's nothing to suggest that this is a more dangerous strain of bacteria," Cutrell said. "There's certainly no evidence to suggest that this is a new bacterium."
Experts say there are clear reasons why the number of cases is rising now: First, countries traditionally have increases in mycoplasma pneumonia every few years, so some outbreaks may be part of the seasonal ebb and flow of respiratory illnesses.
"It may be that, in places like Denmark, there was a cycle," said Dr. Amesh Adalja, an infectious disease physician and senior scholar at the Johns Hopkins Center for Health Security.
Fewer social interactions during the pandemic also meant the bacteria didn't have much opportunity to spread in recent years. Now that more children are interacting again in school, daycare, and other social settings, some countries are experiencing resurgences.
China's outbreak in particular doesn't come as a surprise, given the country's strict lockdown measures, said Michael Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota.
"They really had a total shutdown of all infectious diseases," Osterholm said. "So I would have expected exactly what we're seeing now."
Cutrell said some countries could have worse-than-usual outbreaks this year because many young children have not yet been exposed to the bacteria and therefore lack immunity. The same is true for other respiratory illnesses, such as the flu or RSV, he added.
"We're seeing increases in respiratory infections in general, but in particular they look like mycoplasmas," he said. "It's simply because we have a larger group of people who are more susceptible."
Doctors treat mycoplasma pneumonia, like other forms of pneumonia, with antibiotics; however, only certain forms, such as azithromycin (also known as Z-Pak), are effective against it.
Although the disease is relatively easy to treat, Osterholm said staffing shortages or a lack of pediatric beds in hospitals could pose challenges this winter.
"Hospitals can be overwhelmed" by a number of patients "that 10 years ago would have been normal," he said