This post has been updated.

As the mosquito-borne Zika virus moves northward, the Centers for Disease Control and Prevention has issued interim guidelines for evaluating and testing infants in the United States suspected of being infected.

Although only a dozen or so cases have been identified in the United States -- none involving people who were bitten locally -- infectious-disease experts think it's only a matter of time before infected mosquitoes make their way here.

Health officials in Arkansas said Tuesday that they had identified a case in a resident who had recently been out of the country, but they described the case as "mild."

Virginia health officials also said Tuesday they had received confirmation of infection in a resident in the northwest part of the state who'd recently traveled to a country where Zika transmission is ongoing.

Neither case poses a public health risk because the virus isn't spread by casual person-to-person contact.

The World Health Organization has said that it expects Zika to spread to all of the Americas except for Canada and Chile — the two places where type of mosquito that carries the virus doesn't live.

The CDC's new guidelines, which were developed in conjunction with the American Academy of Pediatrics, apply to a broad group of newborns: any baby whose mother during pregnancy traveled to or resided in an area with Zika virus transmission.

As of late Tuesday, those countries are Barbados, Bolivia, Brazil, Cape Verde, Colombia, Ecuador, El Salvador, Guatemala, Guyana, Haiti, Honduras, Mexico, Panama, Paraguay, Suriname, Samoa and Venezuela; the French overseas regions of French Guiana, Guadeloupe and Martinique; the island of Saint Martin; the Dominican Republic; the U.S. Virgin Islands and Puerto Rico. But the list is likely to grow in the coming weeks.

Zika, first discovered in Africa more than 70 years ago, has become a major concern for global health authorities in recent months after Brazilian officials reported it may be the cause for thousands of infants born with brain damage. The CDC is also working with Brazil to investigate a possible link to a rare nerve disorder called Guillain-Barré syndrome that can lead to paralysis. The associations between Zika and Guillain-Barré are alarming because Zika has typically caused only mostly mild, flu-like symptoms.

The document published by the CDC on Tuesday provides a detailed list of tests that health-care providers should give to two groups of infants: infants with microcephaly or intracranial calcifications detected prenatally or at birth, and infants without these findings but whose mothers had positive or inconclusive results for Zika virus infection.

Depending on the circumstances, the tests include cranial ultrasound and eye exams, as well as repeat hearing screening and developmental monitoring. The CDC said providers should contact their state or regional health department to help with testing.

Here is the full document:

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