A frightening new report indicates that officials are doing everything they can to stop the Zika virus from spreading into the United States, but it’s likely to happen anyway.

Dr. Anthony Fauci, who is the director of the National Institute of Allergy and Infectious Diseases at the National Institute of Health, said this week in a press conference that the possibility of the Zika virus spreading from mosquitoes to humans in the United States at some point in the future was “very likely,” according to an ABC Radio report.

However, Fauci noted that officials think the outbreaks will be relatively constrained, similar to regional outbreaks of tropical diseases like dengue fever.

He also said it’s not out of the realm of possibility to control the Aedes aegypti mosquito, which is responsible for spreading the disease in most cases. While it’s tough to control and eliminate the insect, it’s not impossible to reduce the impact, although it requires an “aggressive, concerted effort,” he noted.

Scientists are still learning more about the Zika virus. It has been linked to birth defects in pregnant women, and a recent report has also linked it to a rare form of paralysis. However, not much is known about its long-term effects.

The virus itself is usually mild in the individual that is infected.

“The most common symptoms of Zika are fever, rash, joint pain, and conjunctivitis (red eyes),” the CDC says on its site. “The illness is usually mild with symptoms lasting for several days to a week after being bitten by an infected mosquito. People usually don’t get sick enough to go to the hospital, and they very rarely die of Zika. For this reason, many people might not realize they have been infected. However, Zika virus infection during pregnancy can cause a serious birth defect called microcephaly, as well as other severe fetal brain defects. Once a person has been infected, he or she is likely to be protected from future infections.

“Zika virus was first discovered in 1947 and is named after the Zika Forest in Uganda, it continues. “In 1952, the first human cases of Zika were detected and since then, outbreaks of Zika have been reported in tropical Africa, Southeast Asia, and the Pacific Islands. Zika outbreaks have probably occurred in many locations. Before 2007, at least 14 cases of Zika had been documented, although other cases were likely to have occurred and were not reported. Because the symptoms of Zika are similar to those of many other diseases, many cases may not have been recognized.”