Zika virus was first isolated in the Zika forest of Uganda in 1947. Since then, it has remained mainly in Africa, with small and sporadic outbreaks in Asia. In 2007, a major epidemic was reported on the island of Yap (Micronesia), where nearly 75 % of the population was infected. In May 2015, the Pan American Health Organization (PAHO) issued an alert regarding the first confirmed Zika virus infection in Brazil. Since that time, cases have been reported from a total of 14 countries in the Americas. The World Health Organization has warned that the Zika virus is “spreading explosively” in the Americas, and that as many as four million people could be infected by the end of 2016.
Through mosquito bites
Zika virus (ZIKV) is transmitted to people primarily through the bite of an infected dengue mosquito (Aedes aegypti) or Asian tiger mosquito (Aedes albopictus). These species also spread dengue and chikungunya viruses. They are aggressive daytime biters and live in close association with humans.
From mother to child
Pregnant women can transmit Zika virus to their unborn child during pregnancy. Zika virus has also been detected in breastmilk of infected mothers, but the transmission through breastmilk has not been confirmed. Currently, there are no documented reports of infants getting infected through breastfeeding and no adverse neurological outcomes have been reported in infants that have acquired the virus after birth. The WHO recommends that infants born to mothers with confirmed or suspected Zika infection should follow the normal feeding guidelines (e.g., starting breastfeeding right after birth and continue to exclusively breastfeed during the first six months).
Zika can be transmitted from an infected person to another through unprotected sex. As for many diseases, the infected person does not necessarily know that he or she is infected at the time of sexual intercourse. Condoms can reduce the chance of getting infected with Zika during sex.
Through blood transfusions
Zika virus has been detected in the blood of donors and there have been multiple reports of possible cases of infections through blood donation. The number of reports however is very low, even in countries with ongoing epidemic.
Symptoms of Zika
The most common symptoms of Zika are fever, rash, joint pain, and conjunctivitis (red eyes). The illness is usually mild with symptoms lasting for several days to a week. Only about one in five people who are infected become sick, and for most people the infection causes no symptoms, and leads to no lasting harm. Mosquitoes become infected when they feed on a person already infected with the virus. Scientific concern is currently focused on the possible association of birth defects (microcephaly) to women who become infected while pregnant. Additionally, there are reports of a temporary form of paralysis (Guillain Barré syndrome) that has been reported following exposure to the Zika virus.
How to fight against Zika
Reducing Zika virus infections strongly depends on the control of mosquito vectors by eliminating larval habitat or applying pesticides and limiting person-mosquito contact by using repellents and installing window screens. Mosquito surveillance is a key component of any local integrated vector management program. The goal of mosquito-based surveillance is to quantify human risk by determining the presence and abundance of local vector populations. Biogents mosquito traps such as the BG-Sentinel are very effective in monitoring populations of Ae. aegypti and Ae. albopictus in a local area. For further information on controlling vectors of Zika virus see the CDC publication: Surveillance and Control of Aedes aegypti and Aedes albopictus >
Mosquito surveillance practices such as the number and type of traps used and the frequency of sampling, depend largely on available funding, resources, and trained staff. However, to quickly identify and mitigate a mosquito-borne disease outbreak, establishing and maintaining a local vector surveillance program is critical.