The tools we need to fight COVID-19 by Bill Gates

The coronavirus pandemic pits all of humanity against the virus. The damage to health, wealth, and well-being has already been enormous. This is like a world war, except in this case, we’re all on the same side. Everyone can work together to learn about the disease and develop tools to fight it. I see global innovation as the key to limiting the damage. This includes innovations in testing, treatments, vaccines, and policies to limit the spread while minimizing the damage to economies and well-being.

This memo shares my view of the situation and how we can accelerate these innovations. (Because this post is long, it is also available as a PDF.) The situation changes every day, there is a lot of information available—much of it contradictory—and it can be hard to make sense of all the proposals and ideas you may hear about. It can also sound like we have all the scientific advances needed to re-open the economy, but in fact we do not. Although some of what’s below gets fairly technical, I hope it helps people make sense of what is happening, understand the innovations we still need, and make informed decisions about dealing with the pandemic.

Exponential growth and decline

In the first phase of the pandemic, we saw an exponential spread in a number of countries, starting with China and then throughout Asia, Europe, and the United States. The number of infections was doubling many times every month. If people’s behavior had not changed, then most of the population would have been infected. By changing behavior, many countries have gotten the infection rate to plateau and start to come down.

Exponential growth is not intuitive. If you say that 2 percent of the population is infected and this will double every eight days, most people won’t immediately figure out that in 40 days, the majority of the population will be infected. The big benefit of the behavior change is to reduce the infection rate dramatically so that, instead of doubling every eight days, it goes down every eight days.

We use something called the reproduction rate, or R0 (pronounced “are-nought”), to calculate how many new infections are caused by an earlier infection. R0 is hard to measure, but we know it’s below 1.0 wherever the number of cases is going down and above 1.0 wherever the number of cases is going up. And what may appear to be a small difference in R0 can lead to very large changes.

If every infection goes from causing 2.0 cases to only causing 0.7 infections, then after 40 days you have one-sixth as many infections instead of 32 times as many. That’s 192 times fewer cases. Here’s another way to think about it: If you started with 100 infections in a community, after 40 days you would end up with 17 infections at the lower R0 and 3,200 at the higher one. Experts are debating now just how long to keep R0 very low to drive down the number of cases before opening up begins.

Exponential decline is even less intuitive. A lot of people will be stunned that in many places we will go from hospitals being overloaded in April to having lots of empty beds in July. The whiplash will be confusing, but it is inevitable from the exponential nature of infection.

As we get into the summer, some locations that maintain behavior change will experience exponential decline. However, as behavior goes back to normal, some locations will stutter along with persistent clusters of infections and some will go back into exponential growth. The picture will be more complex than it is today, with a lot of heterogeneity.

Have we overreacted?

It is reasonable for people to ask whether the behavior change was necessary. Overwhelmingly, the answer is yes. There might be a few areas where the number of cases would never have gotten large numbers of infections and deaths, but there was no way to know in advance which areas those would be. The change allowed us to avoid many millions of deaths and extreme overload of the hospitals, which would also have increased deaths from other causes.

The economic cost that has been paid to reduce the infection rate is unprecedented. The drop in employment is faster than anything we have ever experienced. Entire sectors of the economy are shut down. It is important to realize that this is not just the result of government policies restricting activities. When people hear that an infectious disease is spreading widely, they change their behavior. There was never a choice to have the strong economy of 2019 in 2020.

Most people would have chosen not to go to work or restaurants or take trips, to avoid getting infected or infecting older people in their household. The government requirements made sure that enough people changed their behavior to get the reproduction rate below 1.0, which is necessary to then have the opportunity to resume some activities.

The wealthier countries are seeing reduced infections and starting to think about how to open up. Even as a government relaxes restrictions on behavior, not everyone will immediately resume the activities that are allowed. It will take a lot of good communication so that people understand what the risks are and feel comfortable going back to work or school. This will be a gradual process, with some people immediately doing everything that is allowed and others taking it more slowly. Some employers will take a number of months before they require workers to come back. Some people will want the restrictions lifted more rapidly and may choose to break the rules, which will put everyone at risk. Leaders should encourage compliance.

Differences among countries

The pandemic has not affected all countries equally. China was where the first infection took place. They were able to use stringent isolation and extensive testing to stop most of the spread. The wealthier countries, which have more people coming in from all over the world, were the next to be affected. The countries that reacted quickly to do lots of testing and isolation avoided large-scale infection. The benefits of early action also meant that these countries didn’t have to shut down their economies as much as others.

The ability to do testing well explains a lot of the variation. It is impossible to defeat an enemy we cannot see. So testing is critical to getting the disease under control and beginning to re-open the economy.

So far, developing countries like India and Nigeria account for a small portion of the reported global infections. One of the priorities for our foundation has been to help ramp up the testing in these countries so they know their situation. With luck, some factors that we don’t understand yet, like how weather might affect the virus’s spread, will prevent large-scale infection in these countries.

However, our assumption should be that the disease dynamics are the same as in other countries. Even though their populations are disproportionately young—which would tend to mean fewer deaths from COVID-19—this advantage is almost certainly offset by the fact that many low-income people’s immune systems are weakened by conditions like malnutrition or HIV. And the less developed a country’s economy is, the harder it is to make the behavior changes that reduce the the virus's reproduction rate. If you live in an urban slum and do informal work to earn enough to feed your family every day, you won’t find it easy to avoid contact with other people. Also, the health systems in these countries have far less capacity, so even providing oxygen treatment to everyone who needs it will be difficult.

Tragically, it is possible that the total deaths in developing countries will be far higher than in developed countries.

What we need to learn

Our knowledge of the disease will help us with tools and policies. There are a number of key things we still don’t understand.  A number of studies are being done to answer these questions, including one in Seattle done with the University of Washington. The global collaboration on these issues is impressive and we should know a lot more by the summer.

• Is the disease seasonal or weather dependent? Almost all respiratory viruses (a group that includes COVID-19) are seasonal. This would mean there are fewer infections in the summer, which might lull us into complacency when the fall comes. This is a matter of degree. Because we see the novel coronavirus spreading in Australia and other places in the Southern hemisphere, where the seasons are the opposite of ours, we already know the virus is not as seasonal as influenza is.
• How many people who never get symptoms have enough of the virus to infect others? What about people who are recovered and have some residual virus—how infectious are they? Computer models show that if there are a lot of people who are asymptomatic but infectious, it is much harder to open up without a resurgence in cases. There is a lot of disagreement about how much infection comes from these sources, but we do know that many people with the virus don’t report symptoms, and some portion of those might end up transmitting it.
• Why do young people have a lower risk of becoming seriously ill when they get infected? Understanding the dynamics here will help us weigh the risks of opening schools. It is a complicated subject because even if young people don’t get sick as often, they might still spread the disease to others.
• What symptoms indicate you should get tested? Some countries are taking the temperature of lots of people as an initial screening tool. If doing this helps us find more potential cases, we could use it at airports and large gatherings. We need to target the tests we have at the people at greatest risk since we don’t have enough tests for everyone.
• Which activities cause the most risk of infection? People ask me questions about avoiding prepared food or door knobs or public toilets so they can minimize their risk. I wish I knew what to tell them. Judgements will have to be made about different kinds of gatherings like classes or church going and whether some kind of spacing should be required. In places without good sanitation, there may be spread from fecal contamination since people who are infected shed the virus.
• Who is most susceptible to the disease? We know that older people are at much greater risk of both severe illness and death. Understanding how gender, race, and co-morbidities affect this is a work in progress