Zika virus (ZIKV) - Incidence and Trends
To date, 39 countries and territories have confirmed local, vector-borne transmission of Zika virus in the Region of the Americas since 2015 (**Figure 1**). Since the last Pan American Health Organization/ World Health Organization (PAHO/WHO) Zika Epidemiological Update on 19 May 2016, no additional countries or territories confirmed vector-borne autochthonous transmission of Zika virus.
A downward trend of cases of Zika virus disease in Central and South America continues to occur while in most Caribbean countries and territories the trend continues to rise.
As an example, the epidemic curve of arboviruses in Panama is highlighted below.
Panama
The first cases of autochthonous transmission of Zika virus disease in Panama were confirmed in epidemiological week (EW) 47 of 2015 on the island of Ustupu in the Alligandi district, region of Kuna Yala. From EW 47 of 2015 until EW 18 of 2016 Panama has registered 846 suspected cases of Zika virus disease of which 272 were laboratory confirmed. A majority of the cases are from the region of Kuna Yala. During the same period there were 14 laboratory confirmed chikungunya cases and 1,400 confirmed dengue cases reported. The case distribution is demonstrated in Figure 2.
Zika virus disease in pregnant women
The detection of Zika virus disease in pregnant women is being heightened in countries in the Region due to the 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 (**Table 1**); this number remains the same since the last PAHO/WHO Zika Epidemiological Update on 19 May 2016.
Highlighted below are the surveillance results of pregnant women with Zika virus disease in the Dominican Republic.
Dominican Republic
Between EW 1 and EW 17 of 2016, a total of 338 pregnant women suspected with Zika virus disease have been detected in the Dominican Republic. Of the suspected cases, 243 were infected during the first or second trimester of pregnancy and 95 during the third trimester. A total of 49% (34) reside in Santo Domingo, 14% (34) in Azua, and 11% (27) in the National District. See full report.
Congenital syndrome associated with Zika virus infection
No new countries or territories have reported cases of congenital syndrome associated with Zika virus infection (**Table 2**) since the last PAHO/WHO Zika Epidemiological Update on 19 May 2016.
Brazil
According to the Ministry of Health of Brazil, between 22 October 2015 and 21 May 2016, a total of 7,623 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[6]. Of these, the Brazil Ministry of Health confirmed 1,434 cases of microcephaly by clinical, radiological, and/or laboratory methods (208 have been confirmed by laboratory criteria). Out of the total reported cases, 2,932 cases were discarded as being due to non-infectious causes or not fitting the case definition, and 3,257 remain under investigation. The confirmed cases occurred in 517 municipalities, located in 26 out of 27 Federal Units of Brazil.
Between EW 3 and EW 20 of 2016, the greatest number of microcephaly cases were confirmed in EW 4 (134 cases). During the same period the range of cases investigated (confirmed and discarded) were between 80 (EW 12) and 381 (EW 4)(**Figure 3**).
This week when comparing the trend of reported cases of microcephaly and other congenital malformations in the state of Pernambuco, Brazil, analyzed in conjunction with the reported cases of the three circulating arboviruses (chikungunya, dengue and Zika virus) the results stand out.
Since the beginning of 2015 until EW 20 of 2016, Pernambuco shows a bimodal curve of dengue cases with peaks occurring between EW 13 and 15 of 2015 and another peak in EW 7 of 2016. Around these same epidemiological weeks the peak of Zika virus cases was also registered. The first confirmed cases of microcephaly associated with the Zika virus appear 7 to 8 months after the first detection of Zika virus disease cases, reaching a peak in EW 46 of 2015 (**Figure 4**). Considering that the occurrence of cases of microcephaly may follow the same pattern observed in 2015, it may be expected that in 2016 the same increase of cases will be seen between 7 to 8 months after the increase noted in EW 7 of 2016.
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 (Table 3).
Highlighted below is information on the situation regarding neurological syndromes registered in Panama and the Dominican Republic.
Trend of Guillain-Barré syndrome in Panama
In Panama, since 2010 to date, there is an increasing trend in the rate of GBS cases ranging between 0.08 and 0.43 per 100,000 population (Figure 5). Thus far in 2016, a total of six neurological syndromes have been registered, 5 of which have a clinical picture compatible with GBS and one with cerebellitis. In 3 of the cases (2 GBS and 1 cerebillitis) prior infection with Zika virus has been confirmed by RT-PCR.
Trend of Guillain-Barré syndrome in the Dominican Republic
In the Dominican Republic, since the beginning of the intensified surveillance of Zika virus disease in EW 1 until EW 17 of 2016, there have been 100 cases of GBS detected, and are suspected of being associated with Zika virus infection. Of those, 42% reside in Santo Domingo, 25% in the National District, 10% in Barahona, and 7% in Azua. To date, there have been six fatal GBS cases suspected of Zika virus disease.
In Figure 6, a significant increase in cases of GBS starting in EW 14 of 2016 is shown; this may be related to the resolution issued by the Dominican Republic Ministry of Public Health on 14 April, establishing a mandatory notification of cases of GBS, microcephaly, and other congenital abnormalities related to the Zika virus epidemic.