Since Zika was first detected in the Americas in May 2015, PAHO/WHO has published counts of Zika cases that the 52 countries and territories of the Americas have reported directly or published in national bulletins. PAHO/WHO continues to do everything possible to capture Zika surveillance data and consolidate it for public health purposes.
Notifiable diseases like Zika are largely detected through passive surveillance systems that identify cases in people seeking medical care at participating health facilities. However, given the high proportion of asymptomatic individuals among those infected with the Zika virus, the lack of specificity in clinical presentation among cases, and the complexity of laboratory diagnosis in a context of co-circulation of closely related viruses, detecting the Zika virus presents many challenges. While efforts are directed towards improving the sensitivity of surveillance systems, the lack of detection is not a guarantee that the Zika virus is not in circulation or that local transmission has been interrupted.
