In 2015 and 2016, the word Zika evoked fear in pregnant women living or traveling to tropical areas of the Americas. In countries where the mosquito-borne disease spread, babies of some infected mothers were being born with microcephaly, marked by abnormally small heads, brain damage and a future of developmental problems.
The Zika virus infection is caused by the bite of an infected Aedes aegypti mosquito, usually causing rash, mild fever, conjunctivitis, and muscle pain. One in four infected people develop symptoms and, among those who do, the disease is usually mild and can last 2-7 days.
But a new picture emerged in the State of Pernambuco in north-eastern Brazil in September 2015, when epidemiologists suspected that Zika could be behind a surge of babies born with microcephaly.
The virus was first isolated in 1947 in the Zika forest of Uganda, giving it its name. For decades, it remained mainly in Africa, with small and sporadic outbreaks in Asia.
In 2007, a major epidemic was reported on the island of Yap in Micronesia, where nearly 75% of the population was infected, and from there it appeared in Latin America, in a seemingly more virulent and harmful form.
As soon as the Pan American Health Organization (PAHO) and the Global Outbreak Alert and Response Network (GOARN) alerted Brazilian authorities of a highly probable association of Zika and microcephaly, PAHO declared an emergency on 5 December 2015 and started to help countries in the response. Subsequently, the World Health Organization (WHO) declared Zika a Public Health Emergency of International Concern on 1 February 2016, which would last until November 2016.
The challenge the virus would bring to the region was formidable: by the end of 2016, 48 countries and territories in the Americas had reported more than 532,000 suspected infections, including 175,063 confirmed cases. In addition, 22 countries and territories reported 2,439 cases of congenital syndrome associated with Zika, mostly in Brazil.
“The outbreak was a complicated chess game,” said Dr. Sylvain Aldighieri, the PAHO Incident Manager at the time of the Zika epidemic, “with many moving parts, all of which were constantly evolving, making it much more challenging for scientists to study and understand.”
The situation was especially worrying due to the sheer number of vulnerable populations. “Across PAHO member states, we have more than 500 million people living in areas at risk of Zika, Dengue, or Chikungunya, because of the presence of the Aedes Aegypti mosquito,” Dr. Aldighieri added.