Washington health officials have stepped up surveillance for Zika virus, which is racing across Latin American and the Caribbean. But the infection linked to birth defects is not the cause of a cluster of cases here, experts say.

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Amid growing concern about Zika virus — a mosquito-borne infection exploding across Latin America and the Caribbean and raising fears about birth defects — Washington state health officials say they’ve stepped up surveillance, too.

Health-care providers who see sick travelers are being urged to consider possible Zika infections, along with growing cases of dengue fever, chikungunya and other illnesses spread through the bites of the bugs, said Dr. Scott Lindquist, the state’s epidemiologist for communicable disease.

“If you’re thinking dengue or chikungunya, you should also think Zika,” Lindquist said. “It could come in through any of these routes of globalization.”

The increased surveillance was in place even before news this past week that a Texas woman was diagnosed with Zika virus after a trip to El Salvador and federal officials issued a Level 2 alert for pregnant women to consider postponing travel to countries where Zika virus transmission is being seen.

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The alert also applies to women considering pregnancy to consult with their health-care provider before traveling to those areas.

The virus has a possible link to microcephaly, a birth defect in which babies develop abnormally small heads and brains.

It’s not because Zika virus is very likely to show up here — or because it’s a factor in a mysterious cluster of a different type of birth defect, called anencephaly, in Central Washington.

“There’s no link,” Lindquist said.

After a Seattle Times investigation into the cluster of anencephaly cases, many readers heard news reports about the rapid rise of microcephaly cases in Brazil and wondered if there was a connection.

Officials in Brazil said last week they’ve detected 3,500 cases of microcephaly in newborns, and tests have found traces of Zika virus in tissue. Until last year, the country logged about 150 cases of microcephaly each year.

There have been 41 cases of anencephaly in three Central Washington counties since 2010, a rate about five times higher than the national figures. Anencephaly is a fatal disorder that occurs when the neural tube that forms the brain and spinal cord fails to close in early pregnancy, leaving babies missing parts of the brain and skull.

Dr. Robert Coombs, a professor of medicine and virus expert at the University of Washington School of Medicine, said women are obviously looking for an answer, “But the answer isn’t Zika. It isn’t here.”

The possibility of infections from Zika virus and other mosquito-borne viruses, including dengue fever and chikungunya is low, but possible, even in Washington state, Lindquist said.

Health officials tracked 37 combined cases of dengue and chikungunya in Washington in 2015, higher than the 23 reported in 2014 — and far higher than the rare reports in previous years. They were detected in travelers who had visited places such as Hawaii, Mexico or Latin America and fell ill when they returned home.

The viruses generally cause fever, joint pain and rash, though serious complications such as encephalitis or meningitis can occur. Only about a quarter of people infected show signs of disease.

Transmission of Zika virus has been detected in 14 countries and territories in the Western Hemisphere, according to the World Health Organization. The virus was confirmed in Brazil in May and has taken off.

A few cases have been reported in travelers returning to the U.S., including the Houston woman diagnosed this past week after a trip to El Salvador in November. No local transmission has been seen in the U.S., according to the Centers for Disease Control and Prevention (CDC).

A link between Zika and microcephaly has not been proven, but CDC officials said this week they were considering warning pregnant women against travel to countries where Zika is spreading to avoid risk to newborns.

There’s no vaccine for Zika virus, so the only protection is to avoid the bites of mosquitoes by wearing appropriate clothing, using insect repellent and keeping mosquitoes outside, the CDC says.

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