Every location with COVID-19 cases needs to act immediately by issuing and vigorously enforcing a stay-at-home order. And everyone – every single person – needs to comply with these orders so we can stop the transmission of this virus. This is the only way we can bring this epidemic under control and save thousands – perhaps millions – of lives. Yes, there is a great economic cost to this endeavor and it demands personal sacrifice on the part of each one of us, unlike anything we have seen since World War II. But the alternative is much, much, much worse.

We can bring back businesses and the economy, we can restore relationships and communities – but we cannot bring back lives. And we cannot go into the past and dial back the epidemic.

If we do what is needed now we can eventually return to normal. It will be a new normal, one that requires an investment in public health systems to detect and rapidly respond to contagion of all kinds. This new normal will allow us to go back to restaurants and stores, re-open business, enjoy the company of others, and all the things that we have grown to love about life. However, to get there we need to commit to the drastic action that is needed.

Here’s why. COVID-19 is very contagious and very deadly. Cases and deaths are not just increasing ­– they are accelerating. Cases in communities are doubling about every 3 days, meaning that by the end of this week the number of cases in your community will double, and then double again. At this rate of increase, one case becomes 100 in less than 20 days and becomes 1,000 in about a month. Nothing else in our daily life does acts like this. If it COVID-19 goes uncontrolled, health officials predict that COVID-19 will infect 80% of the world’s population within a year.

If we do not act immediately and aggressively, for our individual cities this could mean a rapid increase in cases and deaths. In New York City, where cases and deaths are doubling every two days, there may be 100,000 cases and 500 deaths by early next week. In Chicago, where epidemic spread started later than in New York City, we will get to 100,000 cases in about 3 weeks. With numbers like this, both cities – and many other areas of the country – will experience overwhelmed hospitals that increase the risk of fatalities significantly.

Without an order and enforcement to stay at home, these cities will experience a different trajectory than cities that put in place such orders early on, such as Seattle and San Francisco. Italy, a country with a very highly rated and well-regarded health system, went from just 3 cases 2 months ago to nearly 800 deaths in a single day last Saturday. However, not all places in Italy had the same fate. In the Lombardy region, where the community spread started in Italy, the province of Lodi quickly implemented a lock down on February 23. Bergamo, on the other hand, waited until the national lockdown on March 9. Lodi was able to flatten the curve, but in Bergamo the epidemic spread aggressively and out of control.

No place on earth has put in place a lockdown order and regretted it. The only regret is wishing they had done it earlier. People from these places around the world – China, Italy, South Korea ­– as if people coming from our future, are telling us to do it now.

There is some good news: COVID-19 can be stopped and reversed. And communities in Asia and Europe have shown us what works. In order to turn this around, we must completely lock down all but essential activity. When we do this, in about two weeks the rate of new cases will begin to go down and we will begin to see a light at the end of the tunnel. When we reach this point, we will be winning and everything will be different. We can start to prepare for life re-opening and for the return to our communities.

But we are not at this point now. We cannot see this light until we see the curve drop the other way. And the curve won’t go the other way until we are sure that we have stopped all or almost all spread – because unless you do case finding and contact tracing to stop each case immediately, within weeks every new case can become 1000.

We are all anxious for the return to normal life, but we cannot open up until we know that we are safe. And the only way to be assured a community is ready to open up is by requiring communities to prove it. If a community can show that they have few or no new cases, their health department is effective at case finding and contact tracing, all cases are in isolation, and testing is widespread, then a community can leave lockdown. In the Hubei province in China, which went on lockdown on January 23, they are now beginning to emerge to normal life.

Ebola shows up frequently in Africa, but it has never become a pandemic because public health systems exist there, with workers who are able to stop fresh outbreaks before they goe too far. I have worked in over twenty five countries to combat epidemics of tuberculosis, cholera, AIDS, SARS and Ebola, and served as the Director of Intervention at the World Health Organization. I have seen the power of public health to quickly set up systems that ensure diseases cannot spread in a community. We can stop COVID-19 and return to a new normal.

As individuals, we must make a greater commitment to isolation and prevention. When you really feel you are “overdoing it,” overdo it more. We must take no chances, because you cannot reverse exposure. Everything that you have heard recently, do it with dedication and purpose and the realization that all of our lives depend on it. Keep 6 feet from others; don’t shake hands; wash your hands frequently; and most importantly, stay at home unless it is an emergency or you are an essential worker. Because COVID-19 can be spread by people who are non-symptomatic, only by “overdoing it” can you ensure the virus is not transmitting to you and that you are not spreading it. Imagine the thousands of people you can save from COVID-19 by overdoing it today. And tomorrow, and as long as it takes.

It’s too late to stop the COVID-19 epidemic from getting out of control. Only by locking down can we regain control, and we must do it immediately. Do you want your hometown’s fate to be like Lodi or like Bergamo? For every leader and every resident of every community in the US, today is the time to decide.