Here’s what coronavirus does to the body
From blood storms to honeycomb lungs, here’s an organ-by-organ look at how COVID-19 harms humans.
PUBLISHED FEBRUARY 18, 2020
MUCH REMAINS UNKNOWN about the novel coronavirus ripping through China, but one thing is certain. The disease can cast a storm over the whole human body.
Such has been the nature of past zoonotic coronaviruses, ones that hopped from animals to humans like SARS and MERS. Unlike their common-cold-causing cousins, these emergent coronaviruses can spark a viral-induced fire throughout many of a person’s organs, and the new disease—dubbed “COVID-19” by the World Health Organization—is no exception when it is severe.
That helps explain why the COVID-19 epidemic has killed more than 1,800 people, surpassing the SARS death toll in a matter of weeks. While the death rate for COVID-19 appears to be a fifth of SARS, the novel coronavirus has spread faster.
Confirmed cases rose to more than 60,000 last Thursday, nearly a 50 percent jump relative to the prior day, and the tally has since increased by another 13,000. This leap reflects a change in the way Chinese authorities are diagnosing infections instead of a massive shift in the scope of the outbreak. Rather than wait for patients to test positive for the virus, diagnoses now include anyone whose chest scan reveals COVID-19’s distinctive pattern of pneumonia. This method will hopefully allow authorities to isolate and treat patients more quickly.
If this outbreak continues to spread, there’s no telling how harmful it could become. A leading epidemiologist at the University of Hong Kong warned this week that COVID-19 could infect 60 percent of the globe if left unchecked.
On Monday, the Chinese Center for Disease Control and Prevention released clinical details on the first 72,314 patients diagnosed through February 11. The report shows that COVID-19 killed 2.3 percent of patients, meaning it is currently 23 times more fatal than the seasonal flu. Severe disease and deaths were reported in every age group, except kids under nine years old.
The Lungs: Ground zero
For most patients, COVID-19 begins and ends in their lungs, because like the flu, coronaviruses are respiratory diseases.
They spread typically when an infected person coughs or sneezes, spraying droplets that can transmit the virus to anyone in close contact. Coronaviruses also cause flu-like symptoms: Patients might start out with a fever and cough that progresses to pneumonia or worse. (Find out how coronavirus spreads on a plane—and the safest place to sit).
After the SARS outbreak, the World Health Organization reported that the disease typically attacked the lungs in three phases: viral replication, immune hyper-reactivity, and pulmonary destruction.
Not all patients went through all three phases—in fact only 25 percent of SARS patients suffered respiratory failure, the defining signature of severe cases. Likewise, COVID-19, according to early data, causes milder symptoms in about 82 percent of cases, while the remainder are severe or critical.
Look deeper, and the novel coronavirus appears to follow other patterns of SARS, says University of Maryland School of Medicine associate professor Matthew B. Frieman, who studies highly pathogenic coronaviruses.
Meanwhile, countries have been scrambling to evacuate their citizens from a cruise ship that’s been quarantined off the coast of Japan. The Japanese health ministry announced Tuesday that an additional 88 passengers on the ship were diagnosed with COVID-19—bringing the total to 542. Of the more than 300 Americans who have been repatriated from the ship, 14 have tested positive for the coronavirus.
But what actually happens to your body when it is infected by the coronavirus? The new strain is so genetically similar to SARS that it has inherited the title SARS-CoV-2. So combining early research on the new outbreak with past lessons from SARS and MERS can provide an answer.
In the early days of an infection, the novel coronavirus rapidly invades human lung cells. Those lung cells come in two classes: ones that make mucus and ones with hair-like batons called cilia.
Mucus, though gross when outside the body, helps protect lung tissue from pathogens and make sure your breathing organ doesn’t dry out. The cilia cells beat around the mucus, clearing out debris like pollen or viruses.
Frieman explains that SARS loved to infect and kill cilia cells, which then sloughed off and filled patients’ airways with debris and fluids, and he hypothesizes that the same is happening with the novel coronavirus. That’s because the earliest studies on COVID-19 have shown that many patients develop pneumonia in both lungs, accompanied by symptoms like shortness of breath.
That’s when phase two and the immune system kicks in. Aroused by the presence of a viral invader, our bodies step up to fight the disease by flooding the lungs with immune cells to clear away the damage and repair the lung tissue.
When working properly, this inflammatory process is tightly regulated and confined only to infected areas. But sometimes your immune system goes haywire and those cells kill anything in their way, including your healthy tissue.
“So you get more damage instead of less from the immune response,” Frieman says. Even more debris clogs up the lungs, and pneumonia worsens. (Find out how the novel coronavirus compares to flu, Ebola, and other major outbreaks).
During the third phase, lung damage continues to build—which can result in respiratory failure. Even if death doesn’t occur, some patients survive with permanent lung damage. According to the WHO, SARS punched holes in the lungs, giving them “a honeycomb-like appearance”—and these lesions are present in those afflicted by novel coronavirus, too