In the Journals

Travel surveillance and genomics uncover ‘hidden’ Zika outbreak

Nathan D. Grubaugh, PhD,
Nathan D. Grubaugh

Based on an analysis of international travel patterns, mosquito modeling and clinical virus genomic sequencing, researchers said they identified an unreported and undetected Zika outbreak that occurred in Cuba in 2017, according to a recent study published in Cell.

They said the framework they developed can be used not only for Zika, but to detect outbreaks of other emerging pathogens.

“We have been interested in understanding the Zika epidemic since its beginnings in Brazil, and much of our previous work has focused on the Zika outbreak in Florida,” Nathan D. Grubaugh, PhD, assistant professor of epidemiology at the Yale School of Public Health, told Infectious Disease News. “As the larger Zika epidemic in the Americas appeared to be waning toward the end of 2016, we became interested in understanding whether the epidemic was truly gone, or whether ‘hidden’ outbreaks could still be occurring.”

According to Grubaugh, the team devised a framework combining travel surveillance and genomic epidemiology to uncover lingering Zika virus transmission previously missed to investigate if “hidden” Zika outbreaks were still occurring.

According to the study, surveillance showed many travel-associated Zika cases originating from the Caribbean in 2017 that were not captured by local reporting — in fact, more than 98% of cases reported in Florida and Europe between June 2017 and October 2018 originated in Cuba, Grubaugh and colleagues found.

Based on incidence rates in travelers, the researchers estimated that an unreported outbreak in Cuba of between 1,071 and 22,611 unreported cases occurred after the larger epidemic had ended, mostly in 2017. Officially, just 187 laboratory-confirmed cases were reported in Cuba in 2016, and none were reported in 2017, according to the study.

Grubaugh said that by sequencing Zika virus genomes directly from infected travelers, the team was able to reconstruct the timing, dynamics and sources of the outbreak to show that it was delayed by a year because of a delay in the establishment of the virus in Cuba. Using a combination of virus genomics, travel patterns and mosquito modeling, they were able to show that the delay was likely caused by an aggressive vector control campaign.

“Accurate monitoring of infectious diseases is key to understanding and responding to outbreaks. As the Zika epidemic — as well as recent outbreaks of Ebola, pandemic flu and other infectious diseases — have shown, early and rapid pathogen detection is critical in preventing outbreaks from spinning into large-scale epidemics,” Grubaugh said.

“Yet, robust surveillance infrastructures and diagnostic capabilities are lacking in many regions of the world most prone to having outbreaks. As the world is getting increasingly more connected and pathogen sequencing is getting cheaper and more accessible, the combination of travel surveillance and genomic epidemiology will allow us to detect and reconstruct outbreaks in the absence of local data. Such a framework is relevant, not only for monitoring lingering Zika virus transmission, but also more broadly speaking for other human pathogens, including emerging ones and those yet to be discovered.” – by Caitlyn Stulpin

Disclosure: Grubaugh reports no relevant financial disclosures.

Nathan D. Grubaugh, PhD,
Nathan D. Grubaugh

Based on an analysis of international travel patterns, mosquito modeling and clinical virus genomic sequencing, researchers said they identified an unreported and undetected Zika outbreak that occurred in Cuba in 2017, according to a recent study published in Cell.

They said the framework they developed can be used not only for Zika, but to detect outbreaks of other emerging pathogens.

“We have been interested in understanding the Zika epidemic since its beginnings in Brazil, and much of our previous work has focused on the Zika outbreak in Florida,” Nathan D. Grubaugh, PhD, assistant professor of epidemiology at the Yale School of Public Health, told Infectious Disease News. “As the larger Zika epidemic in the Americas appeared to be waning toward the end of 2016, we became interested in understanding whether the epidemic was truly gone, or whether ‘hidden’ outbreaks could still be occurring.”

According to Grubaugh, the team devised a framework combining travel surveillance and genomic epidemiology to uncover lingering Zika virus transmission previously missed to investigate if “hidden” Zika outbreaks were still occurring.

According to the study, surveillance showed many travel-associated Zika cases originating from the Caribbean in 2017 that were not captured by local reporting — in fact, more than 98% of cases reported in Florida and Europe between June 2017 and October 2018 originated in Cuba, Grubaugh and colleagues found.

Based on incidence rates in travelers, the researchers estimated that an unreported outbreak in Cuba of between 1,071 and 22,611 unreported cases occurred after the larger epidemic had ended, mostly in 2017. Officially, just 187 laboratory-confirmed cases were reported in Cuba in 2016, and none were reported in 2017, according to the study.

Grubaugh said that by sequencing Zika virus genomes directly from infected travelers, the team was able to reconstruct the timing, dynamics and sources of the outbreak to show that it was delayed by a year because of a delay in the establishment of the virus in Cuba. Using a combination of virus genomics, travel patterns and mosquito modeling, they were able to show that the delay was likely caused by an aggressive vector control campaign.

“Accurate monitoring of infectious diseases is key to understanding and responding to outbreaks. As the Zika epidemic — as well as recent outbreaks of Ebola, pandemic flu and other infectious diseases — have shown, early and rapid pathogen detection is critical in preventing outbreaks from spinning into large-scale epidemics,” Grubaugh said.

“Yet, robust surveillance infrastructures and diagnostic capabilities are lacking in many regions of the world most prone to having outbreaks. As the world is getting increasingly more connected and pathogen sequencing is getting cheaper and more accessible, the combination of travel surveillance and genomic epidemiology will allow us to detect and reconstruct outbreaks in the absence of local data. Such a framework is relevant, not only for monitoring lingering Zika virus transmission, but also more broadly speaking for other human pathogens, including emerging ones and those yet to be discovered.” – by Caitlyn Stulpin

Disclosure: Grubaugh reports no relevant financial disclosures.

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