Different epidemiological profiles in patients with Zika and dengue infection in Tapachula, Chiapas in Mexico (2016-2018): an observational, prospective cohort study

Abstract

Background: The introduction of Zika and chikungunya to dengue hyperendemic regions increased interest in better understanding characteristics of these infections. We conducted a cohort study in Mexico to evaluate the natural history of Zika infection. We describe here the frequency of Zika, chikungunya and dengue virus infections immediately after Zika introduction in Mexico, and baseline characteristics of participants for each type of infection.

Methods: Prospective, observational cohort evaluating the natural history of Zika virus infection in the Mexico-Guatemala border area. Patients with fever, rash or both, meeting the modified criteria of PAHO for probable Zika cases were enrolled (June 2016-July 2018) and followed-up for 6 months. We collected data on sociodemographic, environmental exposure, clinical and laboratory characteristics. Diagnosis was established based on viral RNA identification in serum and urine samples using RT-PCR for Zika, chikungunya, and dengue. We describe the baseline sociodemographic and environmental exposure characteristics of participants according to diagnosis, and the frequency of these infections over a two-year period immediately after Zika introduction in Mexico.

Results: We enrolled 427 participants. Most patients (n = 307, 65.7%) had an acute illness episode with no identified pathogen (UIE), 37 (8%) Zika, 82 (17.6%) dengue, and 1 (0.2%) chikungunya. In 2016 Zika predominated, declined in 2017 and disappeared in 2018; while dengue increased after 2017. Patients with dengue were more likely to be men, younger, and with lower education than those with Zika and UIE. They also reported closer contact with water sources, and with other people diagnosed with dengue. Participants with Zika reported sexual exposure more frequently than people with dengue and UIE. Zika was more likely to be identified in urine while dengue was more likely found in blood in the first seven days of symptoms; but PCR results for both were similar at day 7-14 after symptom onset.

Conclusions: During the first 2 years of Zika introduction to this dengue hyper-endemic region, frequency of Zika peaked and fell over a two-year period; while dengue progressively increased with a predominance in 2018. Different epidemiologic patterns between Zika, dengue and UIE were observed. Trial registration Clinical.Trials.gov (NCT02831699).

Keywords: Chikungunya; Dengue; Emerging diseases; Mexico; Outbreak; Zika.

Map 1

Location of A the State of Chiapas, Mexico in B the border with Guatemala, where C the city of Tapachula is located. Participants were enrolled in 4 participating health care centers and lived in the urban area of Tapachula and 14 rural municipalities in its periphery (C). The red dots in maps C and D indicate the neigborhood or communities of residence of participants. The numbers in black in map C indicate the quantity of participants living in the community enrolled in the study. Each red dot in map E represent an individual participant distributed in the communities around the city of Tapachula. Map developed by Taller de Analisis Espacial (http://taearquitectos.com.mx/) using OpenStreetMap ( https://www.openstreetmap.org/#map=5/38.007/-95.844) and QGIS 3.2 (https://qgis.org/en/site/about/index.html) themed with own data. QGIS is a free and open-source General Public License (GNU) Geografic Information System (GIS). OpenStreetMap (OSM) is a free Open Database Licence (ODbl) editable map of the world

Fig. 1

Screening and enrollment of patients with symptoms compatible with Zika infection in Tapachula, Chiapas (cohort Zik01. Mexico, 2016–2018). Description: Flow diagram showing screening and enrollment of study population 1 There were 40 (8.6%) participants on whom we did not have enough samples to rule out any of these infections (absence of Zika, chikungunya and dengue in available samples but missing data for at least two time points)

Fig. 2

Proportion of urine and serum samples that tested positive for dengue and Zika viral RNA at baseline (day 0–7 of symptom onset), and follow-up visits at day 3 (days 8–10 of symptoms onset) and 7 (days 7–14 of symptoms onset) after enrollment in (cohort Zik01. Mexico, 2016–2018). Description: Bars figure showing the proportion of patients that tested positive for Zika and dengue at visits on day 0, 3 and 7 after enrollment in the cohort. All samples were tested for dengue and Zika viral RNA at days 14, 28 and 180 days after enrollment but none tested positive. There were no patients with dual infection

Fig. 3

Distribution over time of confirmed cases of Zika, dengue and chikungunya infections, and undefined illness episodes of patients enrolled in the Zik01 cohort between June 2016 and July 2018 in the city of Tapachula, Chiapas in Mexico. Description: Epidemic curves over the 2-year period of enrollment by definitive diagnosis