LULU GARCIA-NAVARRO, HOST:
More than 1,600 people, almost all of them in mainland China, have now died from COVID-19. That's the disease caused by the new coronavirus strain first identified in Wuhan, China. Infections on a cruise ship quarantined in Japan have increased to 355. An elderly American who was among the hundreds of passengers to leave another cruise ship last week has also tested positive after she traveled to Malaysia. The virus has now infected more than 68,000 people worldwide. Most of those cases, though, are described as mild. But what does mild mean? And how does this disease turn fatal? NPR's Maria Godoy reports.
MARIA GODOY, BYLINE: The first symptoms of COVID-19 are pretty common.
CARLOS DEL RIO: Fever, and there's dry cough.
GODOY: Dr. Carlos Del Rio is a professor of medicine and global health at Emory University.
DEL RIO: Then you go on to develop shortness of breath. Some people also have - can get a headache, sore throat.
GODOY: Fatigue has also been reported and, less commonly, diarrhea. Data is still coming out of China. But global health officials say about 80% of cases turn out to be mild - anything from cold-like symptoms to that flu-like feeling of being hit by a train. Doctors say these patients should be monitored. But they don't require serious medical intervention. So how does it turn deadly? Well, the virus attacks the lungs. And in about 20% of patients, infections can get more severe. Dr. Yoko Furuya is an infectious disease specialist at Columbia University Irving Medical Center.
YOKO FURUYA: Because our body senses all of those viruses as basically foreign invaders, that triggers our immune system to sweep in and try to contain and control the virus and stop it from making more and more copies of itself.
GODOY: She says the virus can kill lung cells as it replicates inside them. But the immune system response can also destroy lung tissue and cause inflammation.
FURUYA: That's what can lead to an actual pneumonia.
GODOY: With pneumonia, the air sacs in your lungs become inflamed and may be filled with fluid, making it harder to breathe. Del Rio says it can also make it harder for the lungs to get oxygen to your blood. That triggers a cascade of problems.
DEL RIO: The lack of oxygen leads to more inflammation, more problems in the body that eventually lead - organs need oxygen to function, right? So when you don't have oxygen there, then your liver dies, and your kidney dies.
GODOY: That's what seems to be happening in the most critical cases. According to the World Health Organization, about 3-5% of people end up in intensive care. Many of these patients have trouble breathing on their own. In extreme cases, they need a machine to breathe for them.
FURUYA: From what we know right now, many of the more serious infections have been in people older than 60.
GODOY: Furuya says as we get older, our immune systems get weaker. And for long-term smokers, it could be even worse because their airways and lungs are more vulnerable.
FURUYA: And then there are people with more serious illness from this coronavirus that have had other chronic illnesses, like a - heart disease or diabetes.
GODOY: Furuya says those kinds of underlying medical conditions can make it harder for the body to recover from infections. Preliminary estimates suggest about 2% of COVID-19 cases are fatal. Most deaths appear to be the result of multi-organ failure. But Del Rio notes that it's not just this virus that can bring this on. Just last month, he saw the same thing in a flu patient here in the U.S.
DEL RIO: He went into the doctor. They said, you have the flu. Don't worry. He went home. Two days later, he was in the ER. Five days later, he was very sick and in the ICU.
GODOY: In fact, lots of infectious disease experts have been making comparisons between this new coronavirus and the flu and common cold because it appears to be highly transmissible. What they fear is that, like the flu, COVID-19 could keep coming back year after year. Maria Godoy, NPR News.
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