Pope Francis, who remains hospitalized, has bilateral pneumonia, the Vatican said on Tuesday.
The term simply means pneumonia in both lungs, said Dr. James Musser, director of the center for infectious diseases at the Houston Methodist Research Institute. He added that, without examining a patient, he could not say anything specific about his condition.
In general, pneumonia is an infection of the small airways of the lungs. As the body mounts an inflammatory response, small pockets in the lungs fill with immune cells; symptoms can include fever, cough and shaking chills. To diagnose the illness, a doctor typically asks the patient to say a long “e,” as if the person were singing. Through a stethoscope, the “e” of a pneumonia patient sounds like an “a,” said Dr. Paul Pottinger, a professor of infectious diseases at the University of Washington.
Most people with pneumonia recover well at home and do not need to be hospitalized. But for older people, pneumonia can be “a deadly situation,” infectious disease experts said.
Dr. Peter Chin-Hong, professor of medicine and infectious diseases at the University of California, San Francisco, added that “the mortality rate goes up after age 85.” The pope is 88.
The most likely cause of pneumonia is an infection caused by a bacterium, Streptococcus pneumoniae, according to Dr. Chin-Hong. “The No. 1, 2 and 3 cause of pneumonia is strep pneumonia,” he said.
The illness can respond to antibiotics, but bacteria can sometimes spill out of the lungs and into the rest of the body, resulting in sepsis, a dangerous situation. A vaccine can help mitigate this sepsis risk but does not prevent the condition, Dr. Chin-Hong said.
Dr. Pottinger noted that, although strep pneumonia can involve both lungs, it usually is confined to one lobe of one lung. Most bilateral pneumonia, he said, is caused by viruses, including influenza, or other bacteria. Other causes include respiratory syncytial virus, or R.S.V., Legionella, mycoplasma and chlamydia, Dr. Pottinger said.
He agreed with Dr. Chin-Hong about the likely gravity of the pope’s condition.
“It is a very scary situation,” Dr. Pottinger said.
