Viruses—not bacteria—cause most childhood pneumonia

Pneumonia kills nearly 1 million children every year, but the lung infection’s precise cause is often hard to diagnose, forcing doctors to rely on antibiotics without knowing whether bacteria are to blame. Now, a new study reveals that most childhood pneumonia—some 60% of global cases—is caused by viruses.

An array of bacteria and viruses can invade the lungs to cause pneumonia, clogging the lungs’ delicate air sacs with fluid and reducing the oxygen they can absorb. In children especially, the sheer number of potential pathogens and the location of the infected fluid—deep within the lungs—makes diagnosis difficult.

Now, researchers have a new way to identify the cause of severe pneumonia in children. Over 2 years, researchers took nose and throat swabs as well as blood, sputum, and other fluid samples from 4232 children in Bangladesh, Gambia, Kenya, Mali, South Africa, Thailand, and Zambia, all of whom had severe pneumonia. The researchers analyzed the fluids from each patient to infer the most likely cause of their pneumonia from a list of 30 pathogens.

Viruses accounted for more than 60% of all cases and bacteria accounted for just under 30%, researchers report today in The Lancet. The remaining 10% came from fungi, tuberculosis, and unknown causes. Overall, respiratory syncytial virus (RSV) was the biggest culprit, accounting for nearly one-third of all cases. But the breakdown varied significantly by country and region, as the researchers show in this interactive data visualization.

The emergence of viruses, especially RSV (above), as the primary cause of pneumonia highlights the growing need for new vaccines, the researchers say. They add that if their new diagnostic technique can be scaled up, it might also help reduce the global overuse of antibiotics.