The World Health Organization has declared an international health emergency over the spread of the Zika virus , now known to cause devastating birth defects. The agency expects the virus to spread from northern Argentina to the southern United States by the end of the year, infecting many millions of people. In late July, Florida officials announced what appeared to be the first locally transmitted cases of Zika infection in the continental United States.
The W. All pregnant women who have been to these regions should be tested for the infection, health officials have said, and should refrain from unprotected sex with partners who have visited these regions. The Zika virus has been linked to unusually small heads and brain damage in newborns β called microcephaly β in children born to infected mothers, as well as blindness, deafness, seizures and other congenital defects.
The Zika virus is a mosquito-transmitted infection related to dengue, yellow fever and West Nile virus. About four in five victims have no symptoms, and those who do usually recover within a week. Common symptoms include a fever rarely higher than degrees, an itchy pink rash, bloodshot eyes, sensitivity to light, headaches and joint pains. Only female mosquitoes bite people: they need blood to lay eggs, while males drink plant nectar.
In the female, the virus travels from the gut to the salivary glands and is injected into the next human victim.
When a mosquito bites, it first injects an anti-coagulant saliva so blood does not clog its strawlike proboscis. Zika is spread by mosquitoes of the Aedes genus, which can breed in a pool of water as small as a bottle cap and usually bite in daytime. The yellow fever mosquito, Aedes aegypti, takes several bites for each blood meal and prefers biting people; it accounts for most Zika infections.
