Zika virus - Incidence and trends
To date, 39 countries and territories have confirmed local, vector-borne transmission of Zika virus disease 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 9 June 2016, no additional countries or territories confirmed vector-borne autochthonous transmission of Zika virus.
Highlighted below is the Zika virus disease epidemiological situation in Colombia and El Salvador.
Colombia
In Colombia, since the beginning of the epidemic in epidemiological week (EW) 40 of 2015 to EW 22 of 2016, there have been 91,156 suspected Zika virus disease cases reported and 8,221 (9%) were laboratory confirmed.
The Zika cases recorded at the national level reflect a gradual decrease (Figure 2); however, in 20 of the 930 at risk municipalities an increase in cases is observed.
According to geographical distribution of cases, 58% of all suspected cases and 53% of the total confirmed cases are from: Valle del Cauca, Norte de Santander, Santander, Tolima, and Huila. These same territorial entities have higher incidence rates than the national incidence rate (277.29 per 100,000 inhabitants at risk) (Figure 3).
El Salvador
Since the notification of the first Zika virus disease in EW 46 of 2015 to EW 22 of 2016, a total of 10,476 suspected and confirmed Zika virus disease cases have been reported, with a peak of cases observed in EW 49 of 2015 (914 cases) and EW 1 of 2016 (1,140 cases), followed by a decreasing trend of case counts (Figure 4).
Zika virus disease in pregnant women
Twenty-one countries and territories in the Americas have reported confirmed and suspected cases of Zika virus disease in pregnant women (Table 1).
Colombia
Since the beginning of the Zika virus epidemic in Colombia, up to EW 22 of 2016, a total of 16,323 suspected cases of Zika virus disease in pregnant women have been reported, of these 5,420 were laboratory confirmed. Of the reported pregnant women confirmed for Zika virus infection, 1,203 (19%) reside in the department of Norte de Santander.
As of EW 17, out of a total of 13,728 pregnant women with suspected or confirmed Zika virus infection, there are 8,442 ongoing pregnancies and 5,287 pregnancies have come to an end. Table 2 shows the trimester in which Zika virus infection occurred in confirmed and suspected cases (Table 2).
Of the 5,287 women whose pregnancies have come to an end, 4,971 were live births and 316 were fetal deaths and stillbirths (68.3% ended in abortion, 29.4% were stillbirths, and 2.2% final outcome is unknown). Out of the pregnancies for which the outcome were fetal deaths and stillbirths, 58.2% of the women had confirmed or suspected Zika virus infection during the first trimester.
El Salvador
In EW 48 of 2015, monitoring of pregnant women for Zika virus infection was implemented in El Salvador. Since then until EW 22 of 2016, a total of 287 pregnant women were recorded (63 in 2015 and 224 in 2016) with suspected Zika virus disease. Of these women, 38 (13%) samples were taken for laboratory testing of Zika virus infection; 3 (8%) out of the 38 tested positive for Zika virus infection. All three women with positive laboratory results have given birth to babies with no congenital anomalies.
As of EW 21, a total of 111 (39%) of the suspected cases of Zika virus disease in pregnant women have given birth to apparently healthy infants with no reported congenital anomalies.
Congenital syndrome associated with Zika virus infection
Since the last PAHO/WHO Zika Epidemiological Update on 9 June 2016, El Salvador, has been added to the list of countries or territories that have reported cases of congenital syndrome associated with Zika virus infection in the Americas (Table 3).
Colombia
Between EW 1 and EW 20 of 2016, the Colombia surveillance system of congenital anomalies had registered 88 cases of microcephaly nationally. On average, Colombia registers 140 microcephaly cases annually (approximately 12 per month). The number registered in 2016 compared with that recorded in the same period of 2015 (45) represents an increase of 49% (Figure 5).
El Salvador
Between EW 1 to EW 22 of 2016, 47 newborns with microcephaly had been registered in El Salvador. On average, from 2012 to 2016, El Salvador has registered 24 cases annually (Table 4). The number registered in 2016 alone represents an increase compared to the data available for previous years.
In 2015, there were 20 microcephaly cases recorded in 8 of the 14 departments of El Salvador; to date, in 2016, microcephaly cases have been recorded in 12 departments.
In one of the 47 microcephaly cases, Zika virus infection was detected.
Guillain-Barré syndrome (GBS) and other neurological disorders
To date, 9 countries and territories 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 has reported an increase in GBS cases, although none of those cases have been confirmed with Zika virus infection. Three other countries and territories have not recorded an increase in GBS but have identified Zika virus-associated cases of GBS (Table 5).
Highlighted below is information on the situation regarding GBS in Brazil and the Dominican Republic.
Colombia
Between EW 50 of 2015 and EW 22 of 2016, there were 567 cases of neurological syndromes (Guillain-Barré syndrome (GBS), ascending polyneuropathy, and similar neurological conditions) reported as suspected of being associated with Zika virus infection nationwide in Colombia; of these 373 cases correspond to GBS. The suspected and confirmed Zika virus disease epidemiological curve and the epidemiological curve of GBS cases show a similar trend (Figure 6).
In addition, there are currently 48 suspected Zika deaths under investigation.