A link between the mosquito-borne Zika virus and a surge in birth defects in Brazil is growing stronger as the U.S. Centers for Disease Control and Prevention (CDC) said Wednesday the virus was found in the placentas of two women who miscarried, and the brains of two newborns who died shortly after birth.

While the agency warned that the link is not yet definite, the director of vector-borne diseases, Dr. Lyle Peterson said that a team of CDC investigators would be traveling to the country over the next few weeks to conduct more studies.

The brain tissue samples tested came from newborns who were born with microcephaly, a condition characterized by smallness of the head and incomplete brain development. Brazil has seen an explosion in cases of babies born with the condition since mid-2015 when the Zika outbreak picked up in the country.

Now, it’s no secret that viral infections in a pregnant mother can affect the unborn child. Take, for example, cytomegalovirus, a common viral infection that can affect almost anyone – often without symptoms. For pregnant women, a CMV infection can be devastating as it is able to cross the placenta into the fetus leading to a whole range of problems including microcephaly, developmental and motor delays, hearing loss and seizures.

Zika virus comes from the same mosquitos that bring us dengue fever and chikungunya, and while it’s not new, it is becoming more prevalent. One could argue that environmental factors, along with global deforestation has caused the mosquito population to become out of control as this virus is now affecting areas in Latin America and the Caribbean where we never saw these kinds of outbreaks.

Zika virus infection is usually mild and symptoms can last for several days to a week. The most common symptoms are fever, rash, joint pain or conjunctivitis (red eyes), according to the CDC. Other symptoms can include muscle pain, headaches, eye pain and vomiting. Currently there is no vaccine to protect against the virus and no cure for it once a person becomes infected.

Officials have confirmed at least eight cases of Zika virus in the United States among residents returning from travel abroad, but at this time, there is no reason for pregnant Americans to worry. However, you may want to think twice about traveling to parts of Latin America and the Caribbean where they have seen recent outbreaks of the virus.

Dr. Manny Alvarez serves as Fox News Channel's senior managing health editor. He also serves as chairman of the department of obstetrics/gynecology and reproductive science at Hackensack University Medical Center in New Jersey. Click here for more information on Dr. Manny's work with Hackensack University Medical Center. Visit AskDrManny.com for more.