State health officials preparing for mosquito season are gearing up for several potential hurdles ahead when it comes to funding efforts aimed at combatting Zika, a virus that can cause devastating birth defects in infants if a woman is infected during her pregnancy.

Funding for Zika-related efforts was held up in Congress last year, when lawmakers delayed approving $1.1 billion for nine months following former President Barack Obama's initial request of $1.9 billion. This year lawmakers are facing additional political pressures that could hammer states when it comes to emergency public health responses: The country is facing potential Obamacare repeal, which includes a "Public Health and Prevention Fund" that provides $1 billion to the Centers for Disease Control and Prevention, and lawmakers also risk a government shutdown if they do not approve a funding resolution by April 28.

Local Zika transmissions were detected only in Florida and Texas last year, but federal officials have warned all states to be on the alert because most infections occurred when people traveled to areas of the world where mosquitoes carried the virus, particularly in Latin America and the Caribbean.

Though Zika may have faded from the headlines in recent months, Peggy Honein, co-lead of the CDC's pregnancy and birth defects task force, told reporters Monday that the incidence of infection hasn't slowed. Each week the CDC receives 30 to 40 reports of new cases, she said.

"We're not seeing any change with that," she said. "That has been relatively stable, so we do see an ongoing need here."

A CDC study published last week found that 51 babies in the U.S. have been born with birth defects and 77 pregnancies affected by the virus resulted in an abortion, stillbirth or miscarriage. The study evaluated infection in 972 women from Jan. 15 to Dec. 27, and did not include results from Puerto Rico, where the U.S. declared a state of emergency in August.

Complicating public health outreach is that the virus can be difficult to identify because most people who are infected don't have any symptoms and it can be spread sexually. In rare cases in adults the virus can lead to Guillain-barre syndrome, which can cause paralysis, or to symptoms similar to multiple sclerosis.

Because of those attributes, the Zika virus poses a vast array of threats to residents, and it requires coordinated efforts among federal, state and local health officials on several fronts, including mosquito abatement, testing suspected cases, tracking infections, caring for pregnant women who may have been infected and making sure that babies born with birth defects are getting the proper testing and care that they need.

The work can be painstaking. In Florida, health officials went door to door to track the virus and asked residents for urine samples.

The Association of State and Territorial Health Officials, or ASTHO, has not released a dollar amount on how much it estimates the various efforts will cost, and it has emphasized that each state will have different needs.

"Quantifying that is tough," Michael Fraser, executive director of ASTHO, said in a call with reporters. "We want to spend a little more time putting that together."

Honein also said that it was difficult to predict what this year's mosquito season would look like.

"The important factor is being very prepared and making sure we're ready so that as it unfolds we are doing the maximum possible to protect pregnant women," she said.

Ongoing funding will be needed for the development of a vaccine. Four vaccines are being funded by the National Institutes of Health, but only one has recently entered stage 2 of its clinical trial, which is the stage that evaluates its effectiveness. Honein said that approval of a vaccine and making it available will take years, and even then it will require further use and testing before it becomes available to pregnant women. Until then, prevention guidance is focused on protection from mosquito bites, using condoms during sex or abstaining from sex.

Last year as Congress delayed funding, the Department of Health and Human Services, which presides over the CDC, redirected some of its resources to Zika, including by pulling from a previous fund that had been set aside for Ebola. This fiscal year, the CDC has spent or committed roughly $285 million of its Zika supplemental funding.

"We are concerned that may run out," Fraser said.

Even after it was approved, the funding stream was not received by many states until months later. Dr. Brenda Fitzgerald, commissioner and state health officer of the Georgia Department of Public Health, said the state began its Zika response in December 2015 but did not receive federal funding until the following year, when it received $2.4 million in July and then another $1.1 million in December. She said the state would need at least three years of funding at the same level.

A potential area of funding in Trump's budget blueprint involves $500 million that would allow states to spend on public health where they have the most need. But Fitzgerald pointed to another provision in the blueprint that called for the creation of a new "Federal Emergency Response Fund" to respond to public health outbreaks such as Zika.

"We hope that becomes a reality," Fitzgerald said.

The blueprint didn't elaborate on the funding amount or where it would come from, but several health officials, including Dr. Tom Frieden, who was director of the CDC under Obama, have proposed creating such a fund as a way to avoid having needed money held up in Congress. A group of bipartisan lawmakers on Monday sent a letter to congressional appropriators requesting $300 million for such a fund.