Zika virus (ZIKV) – Incidence and Trends
To date, 38 countries and territories have confirmed local, vector-borne transmission of Zika virus in the Region of the Americas since 2015. Since the last Pan American Health Organization/ World Health Organization (PAHO/WHO) Zika Epidemiological Update on 5 May 2016, no additional countries or territories confirmed vector-borne autochthonous transmission of Zika virus.
Some countries in the Region of the Americas continue to register a downward trend in new cases of Zika virus disease (suspected and confirmed). This is consistent with seasonal trends observed in corresponding periods in previous years for other mosquito-borne diseases. Conversely, during the same seasonality, in other countries and territories – mainly the Caribbean – an increasing trend is observed.
As an example of the increasing trend of Zika virus disease cases, the epidemiological situation in Guadeloupe is illustrated below.
Guadeloupe
In Guadeloupe, autochthonous cases of Zika virus disease were first detected in epidemiological week (EW) 3 of 2015. The epidemiological curve of suspected Zika virus disease cases shows an increasing trend, with the increase starting in EW 13 onwards, with the highest number of cases reported in EW 17 (850 cases).
Since the beginning of the epidemic until 28 April 2016 a cumulative total of 412 confirmed cases were reported. Laboratory confirmation in Guadeloupe is obtained only for pregnant women and patients with neurological complications.
Zika virus disease in pregnant women
Detection of Zika virus disease in pregnant women is being heightened in countries in the Region due to risk of congenital syndrome associated with Zika virus infection. There are 21 countries and territories in the Americas reporting confirmed and suspected cases of Zika virus disease in pregnant women; this number remains the same since the last PAHO/WHO Zika Epidemiological Update on 5 May 2016. Results of the surveillance of pregnant women with Zika virus disease in Colombia, French Guiana, Guadeloupe, and Martinique are highlighted below.
Colombia
In Colombia, a total of 13,731 pregnant women have been identified with suspected or confirmed Zika virus infection since the beginning of the outbreak up to EW 17 of 2016. Of these, 15 % were laboratory confirmed with Zika virus. The rest presented symptoms consistent with Zika virus disease.
French Guiana
Since the beginning of the outbreak in EW 51 of 2015 until EW 17 of 2016, a total of 340 pregnant women with laboratory confirmed Zika virus disease have been registered in French Guiana. To date, no occurrences of congenital syndrome associated with Zika virus disease have been registered.
Guadeloupe
Since the beginning of the outbreak in EW 3 of 2016 until EW 17 of 2016, Guadeloupe has registered a total of 18 pregnant women with laboratory confirmed Zika virus disease. To date, no occurrences of congenital syndrome associated with Zika virus disease have been registered.
Martinique
Since the beginning of the outbreak in EW 51 of 2015 until EW 17 of 2016, Martinique has registered a total of 205 pregnant women with laboratory confirmed Zika virus disease. In addition, one case of microcephaly and one other fetal anomaly case have been registered there.
Congenital syndrome associated with Zika virus infection
No new countries or territories have reported cases of congenital syndrome associated with Zika virus infection since the last PAHO/WHO Zika Epidemiological Update on 5 May 2016.
Brazil
According to the Ministry of Health of Brazil, between 22 October 2015 and 7 May 2016, a total of 7,438 suspected cases of microcephaly and other congenital malformation of the central nervous system (CNS) have been reported as per Brazil’s Surveillance and Response Protocol[5]. Of these, the Brazil Ministry of Health confirmed 1,326 cases of microcephaly by clinical, radiological and/or laboratory methods (205 have been confirmed by laboratory criteria). Out of the total reported cases, 2,679 cases were discarded as being due to non-infectious causes or not fitting the case definition, and 3,433 remain under investigation. The confirmed cases occurred in 484 municipalities, located in 25 out of 27 Federal Units.
A weekly median of 191 microcephaly cases were investigated (confirmed and discarded) between EW 3 and EW 12 of 2016 and between EW 13 and 18 of 2016 there was a weekly median of 244 cases investigated.
Guillain-Barré syndrome (GBS) and other neurological disorders
To date, 7 countries in the Region have reported an increase in cases of Guillain-Barré syndrome (GBS) with at least one case laboratory confirmed for Zika virus. Paraguay continues to report an increase in GBS cases, none of which have laboratory results confirming Zika virus infection. Five other countries and territories have not recorded increases but identified Zika virus-associated cases of GBS.
Highlighted below is the trend of neurological syndromes registered in Colombia and the increase in reported acute flaccid paralysis (AFP) in children under 15 years of age in Guatemala.
Trend of neurological syndromes in Colombia
Since 15 December 2015 until EW 17 of 2016, there were 496 cases of neurological syndromes reported in Colombia with history of febrile illness consistent with Zika virus infection. Of the total number of neurological syndromes, 65% (323 cases) correspond to GBSThe epidemic curve of neurological syndromes shows a similar distribution to the Zika virus disease cases. The peak of neurological syndrome cases occurred in EW 3 of 2016 while in contrast the peak of Zika virus disease cases occurred in EW 5 of 2016.
With regards to the age distribution of the neurological syndromes registered, the majority (57.5%) are 35 years or older and males accounted for 57% of the cases.
Acute flaccid paralysis trends in Guatemala
In some countries and territories of the Region of the Americas with autochthonous Zika virus transmission, as in Colombia, Ecuador, and Venezuela, there has been an increase in reporting of acute flaccid paralysis (AFP) in children <15 years of age. While AFP is the manifestation of a wide spectrum of diseases, this situation highlights the importance for countries and territories with Zika virus circulation to analyze the trends in reports of AFP and investigate any unusual increase of cases.
As an example, highlighted below is the situation in Guatemala where a growing trend in the rate of AFP notifications in 2016 until EW 17 is compared to the data of 2015. Of note, Guatemala, has not reported an increase of GBS cases to date.