Epidemiology of Zika Virus Infection

Abstract

Long known to be endemic in Africa and Southeast Asia and a rare cause of acute febrile illness, Zika virus (ZIKAV) arose from obscurity when an Asian genotype ZIKAV caused an outbreak of mild febrile illness in 2007 in Yap State, Federated States of Micronesia. Subsequent viral spread in the Pacific led to a large outbreak in French Polynesia commencing in 2013. After its recognition in the Americas through March 2017, the Pan American Health Organization has received reports of >750000 suspected and laboratory-confirmed cases of autochthonous ZIKAV transmission. Outbreaks in most countries in the Americas peaked in early to mid-2016. Increased surveillance in several Southeast Asian counties has led to increased case recognition, including an outbreak in Singapore, and the first reports of birth defects linked to ZIKAV in the region. As of April 2017, the World Health Organization reported 84 countries or territories with current or previous ZIKAV transmission.

Keywords: Africa; Americas; Asia; Pacific; Zika; arbovirus; emerging disease; epidemiology.

Figure 1.

Countries and territories with evidence of current or past transmission of Zika virus (as of March 2017). Introduction of Zika virus before 2015 but transmission interrupted (Easter Island [Chile], Cook Islands, French Polynesia, New Caledonia, Vanuatu).

Figure 2.

Suspected and confirmed Zika virus disease cases in the Americas reported to the Pan American Health Organization [24] by epidemiological week, May 2015 to December 2016.

Figure 3.

Laboratory-confirmed Zika virus disease cases reported from US states and the District of Colombia by month of illness onset, from January 2015 to April 2017 (provisional data, April 2017).