Zika virus is a mosquito-borne virus transmitted by the Aedes Aegypti and Aedes Albopictus mosquitoes. These mosquitoes, which are prevalent in the Caribbean, Central and South America may also transmit other viral infections including Dengue Fever and Chikungunya.
Zika virus causes the acute onset of fever, rash, joint pains, and conjunctivitis and symptoms can last from several days to a week. Roughly one in five of those infected with the virus develop symptomatic disease.
- Prior to 2014, very few travel-associated cases of Zika virus disease were identified in the United States.
- In 2015 and 2016, large outbreaks of Zika virus occurred in the Americas, resulting in an increase in travel-associated cases in US states, widespread transmission in Puerto Rico and the US Virgin Islands, and limited local transmission in Florida and Texas.
- In 2017, the number of reported Zika virus disease cases in the United States started to decline.
- In 2018 and 2019, there have been no reports of Zika virus transmission by mosquitoes in the continental United States.
Symptoms associated with Zika virus (ZIKV) infection are generally mild and most people who become infected do not develop any symptoms. However, since the 2015‒2017 epidemic in the Americas, ZIKV has been recognized as being associated with severe neurological disorders, mainly Guillain-Barré syndrome in adults and congenital Zika syndrome in fetuses and infants, along with other complications including pre-term birth and miscarriage. Since the epidemic in the Americas peaked in the early spring of 2016, a continuous decline in the number of reported ZIKV disease cases has been observed in the majority of countries throughout the Americas and the Caribbean. Moreover, virus transmission appears to have been interrupted in several island territories since 2017 and early 2018. In Asia, retrospective investigations and epidemiological surveillance suggest a wide geographical distribution of ZIKV. In Africa, information about ZIKV circulation remains limited. The travel-related risk of infection primarily depends on the risk of mosquito-borne transmission at the destination, although sexual transmission is also a possible factor. The risk of infection may be high during epidemics, but ongoing virus circulation is expected to be lower in areas where ZIKV circulation is considered endemic. In such endemic areas the risk of exposure is low to medium. As a precautionary principle, areas where ZIKV circulation has been reported historically (but where there is limited capacity for ZIKV disease surveillance and therefore a lack of evidence concerning the current level of transmission) can be considered as having low-to-moderate transmission risk.
If a pregnant woman has no choice but must travel to areas that pose risk for Zika, she should be advised to follow steps to avoid mosquito bites, such as wearing long-sleeved shirts and long pants, using insect repellents that contain DEET or Picaridin, using permethrin-treated clothing and gear, and staying and sleeping in screened indoor air-conditioned rooms. Zika virus is transmitted by day-biting indoor mosquitoes and the challenge is to remind pregnant women to use insect repellent indoors as well as outdoors.