Different epidemiological profiles in patients with Zika and dengue infection in Tapachula, Chiapas in Mexico (2016–2018): an observational, prospective cohort study
Authors: Belaunzarán-Zamudio Pablo F. , Rincón León Héctor Armando , Caballero Sosa Sandra , Ruiz Emilia , Nájera Cancino José Gabriel , de La Rosa Paul Rodriguez , Guerrero Almeida María de Lourdes , Powers John H. , Beigel John H. , Hunsberger Sally , Trujillo Karina , Ramos Pilar , Arteaga-Cabello Fernando J. , López-Roblero Alexander , Valdés-Salgado Raydel , Arroyo-Figueroa Hugo , Becerril Eli , Ruiz-Palacios Guillermo ,   for the Mexican Emerging Infectious Diseases Clinical Research Network (La Red), Regalado Pineda Justino , Rincón-León Héctor Armando , Navarro-Fuentes Karla R. , Caballero-Sosa Sandra , Camas-Durán Francisco , Priego-Smith Zoyla , Ruiz Emilia , Nájera-Cancino José Gabriel , Rodriguez De la Rosa Paul , Sepúlveda-Delgado Jesús , Vera Maloof Alfredo , Trujillo Karina , López-Roblero Alexander , Valdés-Salgado Raydel , Bertucci Yolanda , Trejos Isabel , Villalobos Luis Diego , Belaunzarán-Zamudio Pablo F. , Ramos Pilar , Arteaga-Cabello Fernando J. , Guerrero Lourdes , Ruiz-Palacios Guillermo , Guerra Blas Paola del Carmen , Mendoza-Garcés Luis , Roy Samira Toledo , Arroyo-Figueroa Hugo , Quidgley Peter , Macedo Laura , Becerril Eli , Montenegro Liendo Abelardo , Powers John H. , Beigel John H. , Hunsberger Sally 
Published: August 2021

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).