Infections with the bacteria that causes walking pneumonia have risen significantly this year, particularly among young children, the Centers for Disease Control and Prevention warned this month.
The bacteria, called Mycoplasma pneumoniae, spreads through coughs and sneezes and can cause respiratory illnesses. Cases have risen among adults and children, but the most notable increase has been among children between 2 and 4, which experts say is striking given that the bacteria typically infects older children. Data suggests that doctors have diagnosed a growing number of children in this age group with infections after they sought treatment in emergency rooms for pneumonia.
Despite its name, only around 10 percent of people infected with Mycoplasma pneumoniae actually develop pneumonia, which is a type of lung infection. When the bacteria does cause pneumonia, it tends to be milder than other forms of the illness, which is why it’s called “walking pneumonia.” Still, it can cause a fever, chest pain and other symptoms that persist for weeks, and in rare cases can lead to hospitalization.
There are roughly two million infections with the bacteria each year in the United States, according to C.D.C. estimates. That number is most likely an undercount, though, since many cases are not diagnosed.
Cases seem to be dipping after peaking in late August, but the C.D.C. said it isn’t yet clear whether that decrease will last, and said that people should stay alert to potential symptoms of an infection.
“Providers should be on the lookout for it, and the general public — and especially parents,” said William Edens, lead of the Legionella and atypical pathogens team at the C.D.C.
Why are cases rising?
The C.D.C. and other researchers are investigating, but the cause of the increase isn’t clear yet.
Experts expect some ebb and flow with Mycoplasma pneumoniae infections: Historically, cases have risen around every three to seven years, for reasons doctors are still trying to understand. Researchers also expected case counts to rise after the coronavirus pandemic, when social distancing and other precautions reduced the transmission of Mycoplasma pneumoniae and other pathogens.
But Dr. Edens said that over the last six months, Mycoplasma pneumoniae infections had been higher than they were before the pandemic. The increase in infections among young children is particularly unusual, experts said.
The rise among younger children may be in part because many stayed home during pandemic lockdowns, instead of going to day care or school. That could mean that some children hadn’t encountered the bacteria or built up immunity against it, and are now getting sick, Dr. Edens said.
Tests to detect infections with the bacteria have also become better and more widely used in recent years, said Dr. Benjamin Singer, a pulmonary and critical care specialist at Northwestern Medicine Canning Thoracic Institute. It’s possible that part of the increase is because of increased testing, Dr. Edens said.
The C.D.C. said it was continuing to investigate the uptick in infections and that it would monitor the demographics of those getting sick, the severity of their illnesses and outcomes compared with those who were infected before the pandemic.
What are the symptoms?
In many cases, the bacteria causes symptoms that feel like a prolonged “chest cold,” Dr. Singer said. These can include a dry cough, fever, headaches and fatigue. Children often develop head and ear aches, said Dr. Geoffrey Weinberg, a professor of pediatrics at the University of Rochester School of Medicine & Dentistry.
It can be challenging to distinguish from Covid, the flu or respiratory syncytial virus (better known as R.S.V.). The key difference is that instead of easing after a few days, symptoms from Mycoplasma pneumoniae tend to develop gradually and worsen over a few weeks. Symptoms can stick around for up to a month.
Some patients also develop a rash. In rare cases, infections can trigger asthma attacks or lead to kidney dysfunction and brain swelling. Infections can also become severe in people with compromised immune systems.
How do you prevent and treat an infection?
People with mild infections usually recover on their own, Dr. Singer said. Doctors often treat those who develop pneumonia with a class of antibiotics known as macrolides.
The C.D.C. is closely monitoring for resistance to those antibiotics in the United States. Experts have documented such resistance more frequently in Asia, but it is not common in the United States.
There’s no vaccine against the bacteria, which mainly circulates among people who live together or spend time in close contact, such as classmates. Most people who briefly encounter someone with the bacteria will not get sick.
Covering your face when you cough or sneeze and frequently washing your hands can help curb the spread, doctors said.
“It’s not one of our most transmissible germs that we deal with,” Dr. Weinberg said. “So that’s sort of good news.”
