Dr. Anthony Fauci gives a presentation about the Zika virus in Washington on Wednesday. (Chip Somodevilla/Getty Images)

Tom Frieden is director of the Centers for Disease Control and Prevention. Anthony S. Fauci is director of the National Institute of Allergy and Infectious Diseases at the National Institutes of Health.

The Zika virus presents an unprecedented threat to the people of our nation, especially pregnant women. Thus far, there have been more than 16,800 cases of Zika infection reported to the Centers for Disease Control and Prevention in the United States and its territories, including more than 2,700 on the mainland. Laboratory tests have confirmed that 1,595 pregnant women have been infected with the virus, and tragically, 17 babies have been born in the United States with birth defects related to Zika. Zika has become a major outbreak in Puerto Rico and established active transmission in two neighborhoods in southern Florida. Other areas of the United States, particularly along the Gulf Coast, are especially vulnerable because of the weather this time of year and large numbers of mosquitoes. It is extremely disturbing to think that, as we write this, somewhere in this country a single mosquito bite may be changing the course of people’s lives.

The Post's Brady Dennis talks with Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, about the process of getting a potential Zika vaccine tested and ready for the public. (Video: The Washington Post/Photo: Sammy Dallal for The Washington Post)

We have an obligation to meet the Zika threat and protect this country. Researchers at the National Institutes of Health have moved fullspeed ahead to find and develop a Zika vaccine and start clinical trials. The CDC has created diagnostic tests for Zika and helped state and local health departments track cases and control mosquitoes, and has deployed large numbers of doctors, lab experts, mosquito specialists and others to areas where local transmission of the virus is occurring.

Pending a supplemental appropriation to meet this emerging crisis, the Obama administration has twice repurposed or transferred funding away from other pressing health priorities — more than $670 million in total. This has exacted its own cost. The most recently transferred funds supported the CDC’s work to immunize children, fight HIV/AIDS, and stop other outbreaks. NIH had to take more than $7 million out of its research into fighting cancer and more than $4 million from our work to turn the tide on the illness that claims more American lives than any other: heart disease.

This “robbing Peter to pay Paul” approach to an emerging public health threat is detrimental to both the Zika response and to the important non-Zika activities being tapped. Furthermore, the redirected funding runs out at the end of September. Without additional funds, the path forward is unclear. Our progress against Zika will slow considerably. The CDC will have to reduce emergency response staff and support to communities fighting this virus. NIH may have to delay or halt its work on a vaccine. And it may even be necessary to cut off funding to pharmaceutical companies that have partnered with government to ensure that a vaccine will be widely available once we have completed the clinical trials and the licensing process.

The potential cost of a funding shortfall will be measured in human misery and even death. Every child born with microcephaly as a result of the Zika infection of the mother during pregnancy could require care that costs the family and our health-care system anywhere between $1 million and $10 million over the lifetime of the child. Every child born with microcephaly faces a difficult future, filled with intensive therapy and support. It is a price that no child — no mother, no father, no family — should have to pay, especially given that it can be avoided.

With the right resources, we can develop better ways to combat the mosquito that spreads Zika and other diseases. We can prevent families from having to go through the heartache of having a baby born with severe birth defects. We can find a vaccine that will protect those most at risk.

Congress returns next week. In the past, it has shown that it understands the importance of safeguarding Americans’ health and has supported biomedical research and vital public health priorities. It has proved that it can act in moments of crisis and in our nation’s hours of need. We’re asking Congress to do so again.