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Pacific origins for Brazil Zika outbreak? – Expert Reaction

Posted in Science Alert: Experts Respond on April 13th, 2016.

The current Zika outbreak in Brazil may have had its origins in Polynesia, says new research speculating the virus was brought to South America by Pacific Island canoeing teams competing in Rio in 2014.

The ongoing Zika outbreak in Rio de Janiero, Brazil, has been scrutinized by Brazilian and German scientists who have revealed its possible origin as well as what are ‘classic’ signs of infection.

The research, published in PLOS Neglected Tropical Diseases, includes genetic analysis of several virus samples, indicating that the virus was introduced to Brazil from Asia.

The authors note that this finding is in line with the speculative hypothesis that Zika was introduced to Rio de Janeiro during the 6th World Sprint Championship canoe race in August 2014, which included teams from four Pacific countries (French Polynesia, New Caledonia, Cook Islands, and Easter Island) where the virus circulated during 2014.

Read more about the research on, and expert commentary below.

National and international coverage of the new study includes:

Yahoo NZ News: Rio’s Zika outbreak matches Asian virus, researchers say
TVNZ: Pacific Islanders may’ve carried Zika to Brazil – study
Newshub: Researchers trace origin of Zika virus
New Zealand Herald: Zika virus may have orginated from Pacific Island canoeists
Japan Times: Rio Zika probe points to Pacific island athletes bringing Asia strain in during 2014 canoe event
Daily Mail: Zika Virus may have traveled from Asia to South America from canoeing contest

The SMC collected the following expert commentary:

Prof Michael Baker, Department of Public Health, University of Otago, Wellington, comments:

“This paper describes an explosive outbreak of Zika virus infection in Rio de Janeiro, starting in January 2015 and peaking in May/June of that year. The phylogenetic analysis showed that all of the strains that were typed had the Asian genotype. The authors note that this finding is consistent with the hypothesis that Zika was introduced by participants in a canoe championship in August 2014, which included teams from four Pacific countries where the virus was circulating.

“This hypothesis is speculative. However, it is a reminder that emerging infectious diseases will frequently ‘hitch hike’ across the globe in infected humans, who may be asymptomatic. All that is required is for an infected person who is viraemic (has circulating virus in their blood) to be bitten by a competent vector mosquito and that could be the beginning of an outbreak in that country.

“One implication of these findings is that the large number of visitors to Rio during the Summer Olympics in August may increase the dissemination of Zika to new locations across the globe (subject to many factors, particularly the distribution of suitable vector mosquitoes). This is another reason why it is important that public health officials in Rio take action to control this epidemic and visitors take measures to protect themselves from mosquito bites.”

Prof Philip Hill, Co-Director, Centre for International Health and the Otago Global Health Institute, University of Otago, comments:

“The comment about the origins possibly being in the Pacific is in the ‘free speculation’ section of the discussion. That means it is just speculation as they have done none of the work required to get a genetic fingerprint match for the virus present in any Pacific country.

“My guess is that this study shows that the virus they have found in this small population in Brazil likely originated from Asia-Pacific somewhere and it found its way into this group of people around 2014/15, but it could easily have started off in Asia a long time before then and come from another part of Brazil in 2014/15. You can’t be more specific than that.”

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