Olympic Games
has started. After more than a week of competitions, Zika
infection does not seem to be any longer a major concern for anyone. Yet still
a few weeks ago, Zika seemed to threaten the
existence of the Olympic Games themselves. Distinguished epidemiologists and public health experts
were even suggesting to postpone or relocate the games and some athletes
announced their will not to participate because of the risk of being
infected. Other athletes decided to freeze their sperm as a precautionary
measure. The entire world was looking
at the Olympic Games in Rio with trepidation and alarm.
The pendulum started to swing towards June, when the World Health Organization, finally, realized that August is midwinter in Rio, that is to say, it is not the mosquito season. So, on June 14 the WHO declared "that there is a very low risk of further international spread of Zika virus as a result of the Olympic and Paralympic Games as Brazil will be hosting the Games during the Brazilian winter when the intensity of autochthonous transmission of arboviruses, such as dengue and Zika viruses, will be minimal and is intensifying vector-control measures in and around the venues for the Games which should further reduce the risk of transmission". This official statement did not revoke the alert but just downgraded the emergency crisis level. As a matter of fact, the WHO still recommended that " countries with travelers to and from the Olympic and Paralympic Games should ensure that those travelers are fully informed on the risks of Zika virus infection, the personal protective measures that should be taken to reduce those risks, and the action that they should take if they suspect they have been infected. Countries should also establish protocols for managing returning travelers with Zika virus infection based on WHO guidance". Were these recommendations truly necessary? Actually, on June 9, the European Center for Disease Prevention and Control (ECDC) had already circulated an Olympics risk assessment stating something different from WHO declaration. According to the ECDC gastrointestinal infections were definitely the first risk for travelers to the Olympic Games, while risks related to Zika infection were considered almost negligible. ECDC's approach was confirmed by the US CDC – on July 13 - in its own 2016 Olympic and Paralympic Game risk assessment, which concluded that the worst-case scenario of Zika contagion would likely lead to a small number of cases, if any, in only 4 of the 206 participating countries and consequently "attendance at the Games does not pose a unique or substantive risk for mosquito-borne transmission of Zika virus in excess of that posed by non-Games travel".
Finally, on July 26 - only nine days before the opening of the games - the Annals of Internal Medicine published a model that drastically rectified original catastrophic predictions. Considering, inter alia, that Rio is far from the epicenter of the Zika outbreak, the study argued that the 2016 Olympics definitely represented a low risk event for Zika infection, disease, and transmission. Authors wrote "Our calculation provides worst-case estimates of travel-associated Zika risk by assuming that visitors encounter the same infectious exposures as local residents. Under these pessimistic conditions, we estimate that an individual traveler's probability of acquiring infection in Rio de Janeiro ranges from 1 in 56 300 to 1 in 6200".
Should we wait for the calculation provided by this new model? Probably not. Already on July 2015, the Lancet Infectious Diseases had published a study devoted to dengue transmission during the 2014 FIFA World Cup in Brazil. Dengue is a disease very close to Zika and it is transmitted by the same mosquito that transmits Zika. Brazil has one of the highest rates of dengue infection in the world and in July 2014 the Football World Cup was held in Rio. As today, the public health authorities were worried by the risk of an outbreak, yet of the million foreign tourists who went to Brazil for the sporting event, only three of them contracted dengue (and no one of them in Rio!). It would have been enough to project this data on the current Zika outbreak, to understand that Zika risks were negligible.
Actually, extrapolating dengue 2014 FIFA World Cup data to Zika 2016 Olympic Games, the worst-case scenario is 3.2 Zika infections per 100,000 tourists, while the much more likely scenario is 1.8 cases per million tourists. Indeed, on 10 May 2016, John McConnell, editor of the Lancet Infectious Diseases, wrote "unless new data emerge before August, we can say that compared with the risks usually associated with travel, such as gastrointestinal infections (on which we have written previously), traffic accidents, and falls, Zika virus represents a minimal threat to games visitors". Should public authorities wait August 2016 for reaching the same conclusions? Couldn't they learn from dengue transmission? Is it ever possible that still in June 2016, the WHO seriously warned tourists who were about to travel to Brazil for the Olympic Games?
Since SARS outbreak in 2003, scientists, public health authorities, and the media, have been systematically overestimating the risk of emerging epidemics. Zika and 2016 Olympic Games are just the last episode of an ongoing saga of risk assessment and communication errors. Given the recurrent nature of these episodes, it is likely that these errors are of systematic nature. It is more and more urgent to understand their origin in order to prevent them. Crying wolf is not only the worst way to communicate risks, but it also paves the way for catastrophic failures, once risks eventually materialize.
The pendulum started to swing towards June, when the World Health Organization, finally, realized that August is midwinter in Rio, that is to say, it is not the mosquito season. So, on June 14 the WHO declared "that there is a very low risk of further international spread of Zika virus as a result of the Olympic and Paralympic Games as Brazil will be hosting the Games during the Brazilian winter when the intensity of autochthonous transmission of arboviruses, such as dengue and Zika viruses, will be minimal and is intensifying vector-control measures in and around the venues for the Games which should further reduce the risk of transmission". This official statement did not revoke the alert but just downgraded the emergency crisis level. As a matter of fact, the WHO still recommended that " countries with travelers to and from the Olympic and Paralympic Games should ensure that those travelers are fully informed on the risks of Zika virus infection, the personal protective measures that should be taken to reduce those risks, and the action that they should take if they suspect they have been infected. Countries should also establish protocols for managing returning travelers with Zika virus infection based on WHO guidance". Were these recommendations truly necessary? Actually, on June 9, the European Center for Disease Prevention and Control (ECDC) had already circulated an Olympics risk assessment stating something different from WHO declaration. According to the ECDC gastrointestinal infections were definitely the first risk for travelers to the Olympic Games, while risks related to Zika infection were considered almost negligible. ECDC's approach was confirmed by the US CDC – on July 13 - in its own 2016 Olympic and Paralympic Game risk assessment, which concluded that the worst-case scenario of Zika contagion would likely lead to a small number of cases, if any, in only 4 of the 206 participating countries and consequently "attendance at the Games does not pose a unique or substantive risk for mosquito-borne transmission of Zika virus in excess of that posed by non-Games travel".
Finally, on July 26 - only nine days before the opening of the games - the Annals of Internal Medicine published a model that drastically rectified original catastrophic predictions. Considering, inter alia, that Rio is far from the epicenter of the Zika outbreak, the study argued that the 2016 Olympics definitely represented a low risk event for Zika infection, disease, and transmission. Authors wrote "Our calculation provides worst-case estimates of travel-associated Zika risk by assuming that visitors encounter the same infectious exposures as local residents. Under these pessimistic conditions, we estimate that an individual traveler's probability of acquiring infection in Rio de Janeiro ranges from 1 in 56 300 to 1 in 6200".
Should we wait for the calculation provided by this new model? Probably not. Already on July 2015, the Lancet Infectious Diseases had published a study devoted to dengue transmission during the 2014 FIFA World Cup in Brazil. Dengue is a disease very close to Zika and it is transmitted by the same mosquito that transmits Zika. Brazil has one of the highest rates of dengue infection in the world and in July 2014 the Football World Cup was held in Rio. As today, the public health authorities were worried by the risk of an outbreak, yet of the million foreign tourists who went to Brazil for the sporting event, only three of them contracted dengue (and no one of them in Rio!). It would have been enough to project this data on the current Zika outbreak, to understand that Zika risks were negligible.
Actually, extrapolating dengue 2014 FIFA World Cup data to Zika 2016 Olympic Games, the worst-case scenario is 3.2 Zika infections per 100,000 tourists, while the much more likely scenario is 1.8 cases per million tourists. Indeed, on 10 May 2016, John McConnell, editor of the Lancet Infectious Diseases, wrote "unless new data emerge before August, we can say that compared with the risks usually associated with travel, such as gastrointestinal infections (on which we have written previously), traffic accidents, and falls, Zika virus represents a minimal threat to games visitors". Should public authorities wait August 2016 for reaching the same conclusions? Couldn't they learn from dengue transmission? Is it ever possible that still in June 2016, the WHO seriously warned tourists who were about to travel to Brazil for the Olympic Games?
Since SARS outbreak in 2003, scientists, public health authorities, and the media, have been systematically overestimating the risk of emerging epidemics. Zika and 2016 Olympic Games are just the last episode of an ongoing saga of risk assessment and communication errors. Given the recurrent nature of these episodes, it is likely that these errors are of systematic nature. It is more and more urgent to understand their origin in order to prevent them. Crying wolf is not only the worst way to communicate risks, but it also paves the way for catastrophic failures, once risks eventually materialize.
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