The World Health Organization has declared Zika virus a global health emergency of international concern. It's projected that the virus could infect up to 4 million people this year.
The last global health crisis to rise to that level was the Ebola epidemic, which spanned 2014 and 2015. But unlike Ebola, which cycled in and out of the news for decades, few people had ever heard of Zika virus before last month. The mosquito-borne virus was known to cause mild symptoms like rashes and fevers, but in most infected people - four out of five - Zika didn't produce any symptoms at all.
That was before Brazilian health officials announced last month that they'd seen 4,000 cases over the last year of infants born with microcephaly, a severe birth defect causing small heads and under-developed brains, and that they believed the defects were linked to Zika.
The virus has been recently found in at least 24 countries, and there are reportedly at least 30 cases in the United States - all of them among people who traveled to high-risk regions. The spread of Zika has left many asking why now, and where it came from.
Scott Weaver, director of the Institute for Human Infections and Immunity at the University of Texas Medical Branch, joins Here & Now's Jeremy Hobson from Galveston, Texas, to answer these questions.
10 Facts About Zika Virus From Scott Weaver
- The Zika virus was discovered in Uganda, Africa in 1947, but it is believed that the virus existed much earlier than that.
- It was discovered when looking for yellow fever in monkeys and was found in mosquitoes in 1948.
- Mosquitoes become infected by feeding on animals infected with the virus.
- After mosquitoes contract the virus, there is an incubation period in which the virus spreads through the mosquito, into salivary glands.
- It is unsure as of yet if the Zika virus can be spread from a mosquito to its progeny.
- Between the discovery and 2007, only 14 human infections of Zika virus were documented.
- Studies conducted on populations in Africa and Asia found high levels of immunity towards the Zika virus, suggesting previous undocumented transmission.
- It's expected to take a few years to develop a vaccine or therapeutics for Zika.
- The current strategy to manage Zika is to reduce the mosquito population, including clearing stagnant water where the mosquitoes breed.
- The mosquito that carries Zika virus, aedes aegypti, prefers to be indoors and bite humans throughout the day.
This segment aired on February 1, 2016.