Why It’s Difficult For Viruses To Turn In To Deadly Pandemics

From NPR
May 29, 2018

Zika, bird flu, West Nile virus, Nipah: The world is constantly being warned of a new disease that threatens to wipe out humanity, and then it doesn’t. Why?


The World Health Organization is in the midst of an experimental campaign to vaccinate tens of thousands of people in Congo against Ebola. The country is battling a new outbreak of the disease there. Also in the news – an outbreak of a deadly disease called Nipah in India. These are just some of the latest viruses to raise alarms around the world. Two years ago, it was Zika – before that, bird flu. Health officials say all these viruses have the potential to kill millions, and yet they haven’t. NPR’s Michaeleen Doucleff is here to explain why.

Hi, Michaeleen.


MARTIN: So what’s going on? Why are there so many false alarms, if we can call them that?

DOUCLEFF: Yeah, so first off, I don’t want to minimize the power of these diseases. These are incredibly destructive outbreaks, even when they’re small or just restricted to a small area. For instance, the Ebola outbreak in West Africa killed more than 11,000 people. But for viruses to turn into pandemics that wipe out millions of people, they need two things – a high mortality rate, and they need to spread very easily. And it turns out, for viruses, this is really hard. For instance, Ebola – it’s very deadly but doesn’t actually spread very quickly or well. Same goes for Nipah, the virus that just cropped up in southern India. It kills up to 70 percent of people infected, but it also doesn’t spread very well.

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