As the new coronavirus spreads around the world, one serious complication of the infection crops up again and again: severe cases of Covid19 are slipping into pneumonia — a serious complication that occurs when the virus invades the lung tissue of the lower respiratory tract.
Pneumonia can be caused by a variety of bacteria, viruses, and (rarely) fungi, as well as the new coronavirus. Severe cases of pneumonia, regardless of pathogen, cause the lungs’ air sacs to fill up with puss and fluid. This prevents oxygen from getting into the bloodstream and carbon dioxide from being cleaned from the bloodstream. “That’s the usual cause of death with severe pneumonia,” Dr. John Wilson, a respiratory physician and former president of the Royal Australasian College of Physicians, told The Guardian Australia.
The coronavirus is not the only virus to cause pneumonia — but pneumonia that results in serious Covid19 cases is likely to be more severe than other types of pneumonia.
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Antibiotics and a vaccine against Streptococcus pneumoniae, the most common cause of bacterial pneumonia, have drastically reduced the illness’s effect on populations. Additionally, bacterial pneumonia is difficult to transmit to others.
By contrast, pneumonia caused by viruses has neither cure nor vaccine, though it typically has approved antiviral, therapeutic treatments. Viral pneumonia — from respiratory syncytial virus (the most common cause of viral pneumonia in children) to influenza virus (the most common cause of viral pneumonia in adults) — is more easily communicated between people but also tends not to be as serious nor as lengthy an illness as bacterial pneumonia, according to the American Lung Association.
That said, because of a global lack of access to vaccines and antibiotic cures for bacterial pneumonia, and complications from malnutrition and air pollution, pneumonia of all types combined caused 2.5 million deaths globally in 2017, mostly among the very young.
Pneumonia caused by the new coronavirus, however, is a different beast. It manifests as the most severe form of Covid19, mostly among patients who are elderly or those with underlying conditions. While not all Covid19 cases develop into pneumonia — and not all that do are fatal — in roughly three months, Covid19 has killed more than 20,000 people globally, with the number only expected to increase exponentially as the pandemic spreads.
And unlike other viral pneumonia, Covid19 pneumonia has no approved or proven, effective therapeutic treatments yet (because the illness itself is so new it has no standard treatment), which leaves health care providers with little to do but watch and/or improvise ways to slow its progression (the latter of which is ethically dubious outside of organized trials). Plus, pneumonia tends to manifest as a progression of already severe cases of Covid19, not as a standalone infection. In these cases — roughly 6% of Covid19 patients who sought medical care in Wuhan, the epicenter of the outbreak — the virus spreads from the upper respiratory tract and conquers the lungs.
