There's another serious health reason to steer clear of mosquitoes.

The first case of Zika, a virus spread by mosquitoes and linked to a possible birth defect in newborns, was reported by health officials in Puerto Rico in late December.

"There is no reason for alarm, and the public should continue to take commonsense steps to avoid mosquito bites, like using repellent and wearing long pants and shirts," Puerto Rican Congressman Pedro Pierluisi said in a statement. He said representatives from the Centers for Disease Control and Prevention (CDC) were expected to travel to Puerto Rico in early January to educate local physicians on diagnosis and treatment of the disease.

The most common symptoms of the Zika virus disease are fever, rash, joint pain and conjunctivitis, according to the CDC. The illness is typically mild with symptoms lasting from a few days to a week. However, pregnant women face a more serious threat. Investigators in Brazil are researching a possible link between Zika virus infection in pregnant women and resulting birth defects in their children. Beginning in October 2015, the Brazil Ministry of Health saw a huge increase in the number of cases of infants born with microcephaly, which is a reduced head size. (Children with microcephaly may have developmental delays, speech and balance problems, seizures, learning issues, hyperactivity and other problems, according to the Mayo Clinic.) Since October, there have been roughly 10 times the number of cases typically reported in a year. Some of the babies with microcephaly tested positive for Zika infection.

Although the link between Zika and the birth defect has not been confirmed, the CDC has issued a travel advisory for tourists, especially pregnant women, traveling to Puerto Rico and other affected areas in South America, Central America, the Caribbean and Mexico, asking them to take precautions to protect themselves from mosquito bites.

Zika virus fever was first discovered in Uganda in the 1940s, reports CNN, and it has since become common in parts of Africa. It has spread to the South Pacific and areas of Asia, and most recently to Latin America.

zika transmission mapCountries that have past or current evidence of Zika virus transmission, as of December 2015. (Photo: CDC)

The mosquito culprit

Zika is spread through the bite of the Aedes species of mosquito. These are the same mosquitoes, according to the CDC, that spread dengue and chikungunya viruses. Reports the CDC: "They are aggressive daytime biters, prefer to bite people, and live indoors and outdoors near people."

The virus is spread directly through an infected mosquito bite but may also be spread from an infected mother to her unborn baby, in theory through a blood transfusion, and through sexual intercourse.

Because Aedes mosquitoes are found throughout the world and because of worldwide travel, it's likely that outbreaks will spread to new countries, suggests the CDC.

There is no preventive vaccine or treatment for Zika. The CDC suggests the usual steps to avoid mosquitoes including using insect repellent, wearing long sleeves and pants, and staying in places with air conditioning or that use screens on windows and doors.

"Zika seems to be generally milder that these other viruses," writes Judy Stone, a contributor for Forbes who covers infectious diseases and medicine, "but that will likely change as we learn more. We thought the same when West Nile virus, a member of the same family, emerged."

Mary Jo DiLonardo Mary Jo writes about everything from health to parenting — and anything that helps explain why her dog does what he does.