title: Evidence of the presence of the Zika virus in Mexico since early 2015.
abstract: To assess the possible circulation of Zika virus (ZIKV) prior to the first documented case in Mexico, we reanalyzed the stored samples from the states of Veracruz and Yucatán, which were originally collected to test for dengue (DENV) and chikungunya (CHIKV) but were negative for these viruses despite the symptomatology. The samples were originally collected between the 30 and 46 epidemiological weeks (EW) when the ZIKV was not yet declared as a Public Health Emergency of International Concern (PHEIC). From the total 4016 negative samples, a total of one hundred samples, 50 from Veracruz (CHIK-DENV-) and 50 from Yucatán (4 CHIK-DENV-and 46 CHIK-or DENV-), were tested for Zika virus by using RT-PCR. Results showed that in Veracruz and Yucatán, 20 % (10/50) and 70 % (35/50) were, respectively, ZIKV positive, indicating unequivocally the presence of ZIKV at least since July 2015. We also tested non-confirmed suspect measles cases from early 2015 for ZIKV by RT-PCR. Remarkably in 11 Mexican states, 86 % (18/21) were positive with the earlier symptoms onset as early as May 2015. Finally, RT-PCR analyses on RNA extracted from Aedes aegypti mosquitoes captured from January to March 2015 showed the presence of ZIKV, strongly suggesting that the vector was already carrying the virus at the start of 2015.
authors.affiliation: Instituto de Diagnóstico y Referencia Epidemiológicos, "Dr. Manuel Martínez Báez", Mexico City, Mexico. alberto.diaz@salud.gob.mx.|Facultad de Medicina, Universidad Nacional Autónoma de México, Mexico City, Mexico. alberto.diaz@salud.gob.mx.
authors.forename: José Alberto
authors.initials: JA
authors.lastname: Díaz-Quiñonez
authors.affiliation: Instituto de Diagnóstico y Referencia Epidemiológicos, "Dr. Manuel Martínez Báez", Mexico City, Mexico.
authors.forename: Irma
authors.initials: I
authors.lastname: López-Martínez
authors.affiliation: Instituto de Diagnóstico y Referencia Epidemiológicos, "Dr. Manuel Martínez Báez", Mexico City, Mexico.
authors.forename: Belem
authors.initials: B
authors.lastname: Torres-Longoria
authors.affiliation: Instituto de Diagnóstico y Referencia Epidemiológicos, "Dr. Manuel Martínez Báez", Mexico City, Mexico.
authors.forename: Mauricio
authors.initials: M
authors.lastname: Vázquez-Pichardo
authors.affiliation: Instituto de Diagnóstico y Referencia Epidemiológicos, "Dr. Manuel Martínez Báez", Mexico City, Mexico.
authors.forename: Edith
authors.initials: E
authors.lastname: Cruz-Ramírez
authors.affiliation: Instituto de Diagnóstico y Referencia Epidemiológicos, "Dr. Manuel Martínez Báez", Mexico City, Mexico.
authors.forename: José Ernesto
authors.initials: JE
authors.lastname: Ramírez-González
authors.affiliation: Dirección General de Epidemiología, Mexico City, Mexico.
authors.forename: Cuitláhuac
authors.initials: C
authors.lastname: Ruiz-Matus
authors.affiliation: Facultad de Medicina, Universidad Nacional Autónoma de México, Mexico City, Mexico.|Subsecretaría de Prevención y Promoción de La Salud, Mexico City, Mexico.
authors.forename: Pablo
authors.initials: P
authors.lastname: Kuri-Morales
mesh_terms: D004196:Disease Outbreaks; D049674:History, 21st Century; D006801:Humans; D008800:Mexico / Q000453:epidemiology; D011159:Population Surveillance; D000071244:Zika Virus / Q000235:genetics; D000071243:Zika Virus Infection / Q000453:epidemiology* / Q000266:history / Q000635:transmission / Q000821:virology*
keywords: Mexico; RT-PCR; Retrospective analysis; Zika virus