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expert reaction to suggestion that the Rio Olympic Games should be postponed or moved due to the Zika virus outbreak, and the WHO’s response

A number of scientists have said that, with the ongoing Zika virus outbreak in Brazil, the upcoming Olympic Games should be moved to another venue however the World Health Organization has rebutted the suggestion.


Prof. Paul Reiter, consultant on mosquitoes and mosquito-borne diseases and Professor of Medical Entomology, Pasteur Institute, said:

“It is misleading to suggest there is a danger of introduction of the Zika virus to places where malaria is already present. There are 3500 species of mosquito – the urban transmission of Zika (and dengue, chikungunya and yellow fever) is by two species that have nothing to do with the anophelines that transmit malaria. They are chalk and cheese. It is important to note that none of the 150 experts that signed this letter has expertise is the epidemiology of mosquito-borne arboviruses.

“In my opinion the WHO has made a careful and scientific decision about the Olympic Games. Zika is transmitted by mosquitoes, not by direct contact (apart from some sexual transmission). So there is limited likelihood that there will be transmission between attendees during the games.

“Granted, there may be people who acquire the virus and travel to other parts of the tropics/sub-tropics and thereby start local transmission. But we must remember that the virus is already being transmitted in 60 countries, and that it was originally an African virus.”


Dr Derek Gatherer, Lecturer in the Division of Biomedical and Life Sciences, Lancaster University, said:

“The call by the signatories to the letter, for postponement or relocation of the Olympic Games, is unjustified.  The letter contains at least two major factual errors. Their statement that “Zika virus harms health in ways that science has not observed before” is incorrect.  Recent experiments on laboratory mice, on brain organoids and in neuronal tissue culture, as well as detailed observation of the clinical manifestations of Zika-associated microcephaly in foetuses and infants, show that Zika can be categorised with other TORCH-syndrome pathogens.  TORCH is an acronym for “Toxoplasma, Rubella, Cytomegalovirus, Herpes”, all agents which cause similar defects in foetuses when the mothers are exposed in pregnancy.  Zika is the only TORCH-like pathogen that is spread by mosquito bites, but there is nothing novel in the clinical presentation in foetuses, as far as we currently know.

“The letter also claims that “most of South Asia and Africa” are “as yet unaffected places“. That is not true. A wide body of literature going back to the 1940s has shown that humans and often also monkey populations in several African and Asian countries have antibodies to Zika virus. These studies need to be repeated to determine the current levels of immunity, but it is very likely that many parts of the tropical world have already seen Zika virus in the past and there will probably be considerable herd immunity in the human population.

“Aside from the errors of fact, the letter implies that the African Nations Cup relocation due to the Ebola outbreak provides an appropriate model for the Olympics. But Zika is not Ebola. If one wishes to draw comparisons with other diseases, the closest is rubella. Brazil has many of the typical diseases found in the tropical world, including malaria and dengue as well as levels of HIV about twice as high as the UK. These are all things that travellers and athletes need to prepare for. All are clinically more serious than Zika, but none has been proposed as a reason to cancel the event. Individual risk assessment and appropriate precautions are the best strategy for all concerned. Pregnant women, those planning pregnancy and those predisposed to Guillain-Barre syndrome perhaps would be best advised to stay away. Others groups simply need to monitor their health carefully during their visit, use insect repellant and avoid risky sexual behaviour. All travellers with fever and/or rash during or after their trip need to report for assessment of its cause. If these principles are observed, there is no reason why the Olympics cannot take place.”


Prof. Jonathan Ball, Professor of Molecular Virology, University of Nottingham, said:

“We live in an incredibly interconnected world, global travel and trade are daily activities that offer Zika virus an opportunity to spread. By comparison to these routine activities, the increased risk that the olympics poses is a drop in the ocean.

“But we can’t be dismissive – people need still to take care to try to avoid further spread and human disease. That means avoiding mosquito bites by covering up and using DEET-containing insect repellent, and avoiding those places experiencing outbreaks if you are pregnant or might become pregnant.”



Declared interests

Prof. Paul Reiter: “I am not in any monetary relationship with Oxitec. However, as a professional, I have been enthusiastic about their technology for many years and act as an advisor on mosquito biology and behaviour. My direct involvement with them has been as follows: In 2005 they funded a PhD student to work on male dispersal. He worked with the Asian Tiger mosquito (not a transgenic; there was none of this species). Most of his work was on Reunion Island (no Ae. aegypti there). Apart from their obvious interest in the results, Oxitec had no involvement in the study. I also had a post-doc who worked for two years in a laboratory study on mating behaviour of the transgenic vs wild type. She was mainly funded by the Institut Pasteur.”

Dr Derek Gatherer: “No relevant conflict of interests concerning Zika virus.  I have participated in a WHO project on Ebola diagnostics, but have received no grant or other financial reward from the WHO for that, or any other work, or on any other occasion.”

Prof. Jonathan Ball has no conflicts of interest.

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