Public health emergencies are a fact of life in a world as interconnected as ours. In just the past five years we have witnessed unexpected outbreaks of devastating diseases—Ebola, chikungunya, yellow fever and Zika—each of which has spread far beyond its historical geographical range. No one can say what the next large-scale emergency will be, whom it will affect or when it will strike, but we do know that it is inevitable. Yet the U.S. is woefully unprepared to meet this threat because it does not set aside money to beat back an outbreak before it can spread.

The U.S. used to have a robust national public health emergency fund, first created by Congress in the 1980s, but its balance has since dwindled to a paltry $57,000—enough to buy a few thousand first aid kits but not much else. What we need is more on the order of several hundred million to $1 billion in new funding that is always and immediately available and is replenished whenever it becomes depleted.

A mechanism is already in place to deal with natural disasters such as earthquakes and floods. The Federal Emergency Management Agency is preauthorized to disburse hundreds of millions of dollars to pay for debris removal, for example, when state or local budgets become overwhelmed by a weather emergency.

Creating a similar “rainy day” fund—and providing the Centers for Disease Control and Prevention with permission to use it in advance—could save lives and money, both at home and overseas. There have been some moves in this direction. President Donald Trump's general budget proposal for 2018 includes such a fund. But it does not give any dollar figures, and the health care bill passed by the House of Representatives in May cuts at least $1 billion from annual public health funding.

The idea behind an emergency fund is not to displace efforts to combat infectious disease but to ramp them up to meet a crushing temporary need. During an outbreak the CDC can call on many doctors and nurses to work without pay, but the costs of transportation, medical supplies and protective equipment still have to be covered. The surge in patients typically increases the need for laboratory testing or surveillance of insects, rodents or other carriers of illness—extra requirements that can be met by short-term contracts with commercial companies.

Thomas Frieden, former director of the CDC, estimates that 90 percent of the Ebola deaths that occurred in West Africa in 2014 and 2015 could have been prevented if the agency had been able to unleash a massive effort right away. In July 2014 he estimates that an additional 300 beds to treat Ebola patients would have been enough to stop the illness from spreading. But July was also approaching the end of the fiscal year for the U.S. government, and there was not enough flexibility in the CDC's budget to finance the necessary response. By November, after Congress made further money available, more than 3,000 beds were needed to treat everyone who had become sick.

When Zika hit the southern U.S. and Puerto Rico in 2016, health officials had to go back to Congress to ask for funds for the new emergency. Months went by without action as some legislators wrangled over the role Planned Parenthood might play in the endeavor, among other things. Local health officials reportedly put other critical programs on hold to deal with the new threat.

Legislators from both the Democratic and Republican parties have recognized the problem and are trying to do something about it. Senator Bill Cassidy of Louisiana, a Republican, introduced the Public Health Emergency Response and Accountability Act last year and again in January 2017 to create a more robust national health emergency fund that would tie current funding to amounts spent on previous public health emergencies. In 2016 Representative Rosa DeLauro of Connecticut, a Democrat, called for a one-time appropriation of $5 billion for emergency health and is planning to do so again this year. But introducing legislation (or making a vague promise in the president's budget) does not help if Congress fails to pass it. Lawmakers need to follow through by approving one or both of the proposed measures for the president to sign to ensure that the money will be there when the next public health emergency strikes.