With the stock markets tanking around the world, travel restricted and large events canceled because of Covid-19, Bill Gates has just issued a stark warning to the world's governments. In a new Gates Notes blog post, he writes that the coronavirus could be a once-in-a-century pandemic equal to the devastating 1918 influenza pandemic. That flu had a 2 percent mortality rate. Before it was done, it had killed between 50 and 100 million people worldwide.

"Global health experts have been saying for years that another pandemic rivalling the speed and severity of the 1918 influenza epidemic wasn't a matter of if but when," Gates writes. Which is why, in the past few years, the Bill & Melinda Gates Foundation has devoted some of its resources to helping the world prepare for such a pandemic.

Will Covid-19 really be as bad as the 1918 flu? It might be, Gates believes. "In the past week, COVID-19 has started to behave a lot like the once-in-a-century pathogen we've been worried about," he writes. "I hope it's not that bad, but we should assume that it will be until we know otherwise." There are two truly frightening things about Covid-19, he writes. The first is its mortality rate, which current estimates place at around 1 percent. That makes it many times deadlier than the seasonal flu we see every year, and about half as deadly as the 1918 flu. And although the first person to die of the coronavirus in the U.S. did have health issues, the virus appears capable of killing perfectly healthy adults, such as Li Wenliang, the Wuhan doctor who came to prominence after Chinese authorities rebuked him for telling his colleagues about the new virus he was seeing.

But it's even scarier that the coronavirus appears to be contagious for up to two weeks before infected people show any symptoms at all, which means they're very likely to pass the virus along. Gates writes that the average person who's infected infects two to three others. "That's an exponential rate of increase," he writes.

All of this is why the Gates Foundation has already committed up to $100 million for fighting the coronavirus. But, he writes, billionaires can't solve this problem alone. Governments need to take action -- and now -- to avert a severe global pandemic. It was clear to infectious disease experts even before Covid-19 that the world's health systems are not up the challenge of a severe global pandemic. But they can be. "The good news is that national, state, and local governments and public health agencies can take steps over the next few weeks to slow the spread of COVID-19," he writes. Here's how.

1. Richer countries must help poorer ones.

The developing or "middle-income" countries where the coronavirus is starting to take hold, such as Iran and India, don't have anything like the healthcare infrastructure that exists in North America or Western Europe. But things will get immeasurably worse when it spreads in earnest to poorer nations such as Haiti, Ethiopia, or Banladesh. Let alone on the border between Turkey and Syria, where a war involving Russia has already created a humanitarian crisis affecting close to a million people even without the virus. 

It's natural for national leaders to think first about protecting their own citizens. The problem with this is that in a world where people routinely travel among nations and where they could be carrying the coronavirus while feeling and appearing perfectly healthy, it will simply not be possible to limit the virus' spread from one country to another. The only hope is to fight it everywhere all at once and that means helping those nations that can't do that effectively on their own. Gates also calls for creating better healthcare systems in poorer nations to help them contain future outbreaks as well.

2. We must get much better at developing and delivering vaccines at scale.

It's hard to overstate the complexity of this challenge. Right now, Gates writes, we need better systems for developing vaccines, better and more open platforms for producing them quickly enough in great enough quantities to turn back a pandemic, better logistics for distributing them and better diplomacy so they can get where they need to go. And we need government money behind vaccine development as well.

We're accustomed to having the pharmaceutical industry research, develop, and produce the medicines we need but that won't work this time, Gates writes, because "pandemic products are extraordinarily high-risk investments." To get pharmaceutical companies to research and make vaccines and medications at the speed and scale needed to contain a pandemic, governments will have to provide some of the funding, he believes.

3. Nations and companies must share information and increase their budgets for fighting pandemics.

In particular, there should be a central database, accessible to all governments and organizations that need it, of current cases and of personnel who are trained and able to help treat the virus or give out vaccines, Gates writes. Put all these recommendations together, and you're talking about a lot of money. He says budgets for fighting the coronavirus and future pandemics "need to be expanded several times over." 

"Obviously, billions of dollars for anti-pandemic efforts is a lot of money. But that's the scale of investment required to solve the problem," he adds. Besides, given both the human suffering and economic pain the coronavirus can cause, "It will be a bargain." 

Last week's stock market plunge may have already erased $4 trillion from the U.S. economy. So I would say he's right.