What's the best way to avoid catching Zika virus? The simplest answer: Don't travel to places where mosquitoes carry and spread it. That list of places is growing, though — the U.S. Centers for Disease Control and Prevention added eight destinations, most of them in the Americas, to the list Friday, as more information emerges about the dangers of the virus, which scientists say could be linked to microcephaly, a birth defect, and potentially paralysis, too.

In addition to recommending that travelers follow "enhanced precautions" (a Level 2 alert, out of three) in Puerto Rico, Brazil, Colombia, El Salvador, French Guiana, Guatemala, Haiti, Honduras, Martinique, Mexico, Panama, Paraguay, Suriname and Venezuela, the CDC said Friday that travelers should take the same care in traveling to Barbados, Bolivia, Ecuador, Guadeloupe, Saint Martin, Guyana, Cape Verde and Samoa.

An outbreak of Zika virus was first noted in Brazil in early 2015. Less than nine months later, the number of reported cases of microcephaly, where a newborn infant's head is abnormally small, typically as a result of abnormal brain development or brain damage, spiked. Although scientists are not certain that Zika virus is the cause, the CDC has described the link as "suggestive of a possible relationship."

Although the virus does not appear to have been transmitted in the United States — yet — the birth of a baby with that defect was reported in Hawaii Jan. 15, the first such birth in the country. The mother was living in Brazil in May 2015.

The countries affected by Zika virus are likely to change, the CDC said, adding, "Specific areas where Zika virus transmission is ongoing are often difficult to determine." The mosquitoes that transmit Zika can also carry other viruses, like chikungunya and dengue, and they are "aggressive daytime biters" that "prefer to bite people," the CDC said.

Because no treatment or vaccine for Zika virus exists, the best way to avoid being infected is to simply not be bitten by mosquitoes carrying it. Symptoms of the virus range from a fever and rash to joint and muscle pain, and red eyes and headache.

Pregnant women, or women trying to become pregnant, are at particular risk if they acquire the virus, because of the potential link between Zika virus and birth defects in babies. "Pregnant women in any trimester should consider postponing travel to the areas where Zika virus transmission is ongoing," the CDC said.

This week, Brazilian disease specialists said more patients, who may have been infected with Zika virus, have been diagnosed this year with Guillain-Barré syndrome, the New York Times reported. Guillain-Barré syndrome is a rare condition where a person's immune system attacks part of the nervous system, leaving them temporarily paralyzed. Researchers have not proved the link between Zika and Guillain-Barré, but researchers and public health agencies are looking into the possibility.