Zika—a virus linked to devastating birth defects—is a serious and urgent threat to the United States. Already, there are more than 900 confirmed cases across U.S. states and territories, and that number is expected to grow as mosquitos carrying the disease spread farther north this summer.

In Puerto Rico, the CDC estimates that 1 in 4 people—hundreds of thousands of American citizens—could become infected by year’s end. For an island in the midst of a financial crisis, with weakening health care infrastructure and insufficient Medicaid funding, that’s a catastrophe in the making.

I recently asked two of my senior campaign advisers to go to Puerto Rico to learn more about how Zika is affecting the island and what we can do to mitigate an outbreak. One thing was clear from their discussions with local health and government officials, visits to impacted neighborhoods, and observations at women’s health clinics: We need more resources to stop the spread of this disease.

First, we must do everything we can to educate the public—especially pregnant women—about the dangers of Zika so that people know to protect themselves against mosquito bites and against sexual transmission of the disease. Puerto Rico has taken an important step by providing education and toolkits to pregnant women through their Women, Infant, and Children (WIC) clinics, but we must do more to raise awareness—in Puerto Rico and across the United States.

Next, we have to develop a rapid diagnostic test for Zika—that’s a critical step, since most people who get the virus never develop symptoms and could unknowingly infect others. We need to invest in treatments and a vaccine. And we have to step up mosquito control and abatement and improve access to health and family planning services.

To put it simply, there’s a lot we need to do—and fast. We don’t yet know everything about this disease, but what we’re learning is alarming. Zika has now been linked to microcephaly, a heartbreaking birth defect that can lead to severe developmental delays and long-term health problems. In Brazil alone, more than 1,000 babies have been born with microcephaly or central nervous system malformations. It is also suspected that, in rare cases, Zika could lead to other neurological problems in adults.

Between travel-related cases, sexual transmission of the disease, and the spread of aedes aegypti mosquitoes, which are native to the southern United States, experts are warning that Zika could spread much farther into the U.S. than initially expected.

We need to do everything we can to fight Zika—but we can’t do that without adequate resources. Congress should immediately provide emergency funding for Zika testing and treatment, mosquito control, family planning, and to support maternal and infant health. It’s up to us to convince them to do the right thing:

Add your name now and call on Congress to address this urgent public health crisis.