I would be more worried about dengue fever than Zika

Earlier this week American cyclist Tejay van Garderen announced he has withdrawn his name from Olympic selection over concerns for his pregnant wife. I decided to have a look at what the actual risks are for athletes and fans a like traveling to Rio this August.

The Zika virus was first discovered in 1947 and was named after the Zika forest in Uganda.1 The virus caused only a limited number of infections until 2007 and 2013, when large outbreaks of Zika were reported in the Yap State, a small island in the Western Pacific, and French Polynesia, respectively.1

The arthropod-borne virus is primarily transmitted to humans through bites from the Aedes aegypti and Aedes albopictus mosquitoes. These species are mostly confined to tropical and subtropical regions and while they are established in the United States, Australia only has a limited population, mostly confined to Northern Queensland.1 Aedes albopictus is of a greater concern as it has the potential to adapt to cooler, densely populated areas and is an aggressive daytime biter.1 Growing concerns over the spread of Zika have also grown from the fact that it can be sexually transmitted.2

 Zika is an RNA virus closely related to other flaviviruses like yellow fever and dengue.3 80% of individuals that become infected never develop any symptoms, while in the other 20% you commonly see fever, rash, conjunctivitis and joint soreness. These symptoms are typically mild and resolve within a few days.3 Of greater concern, is not the primary infection but the complications of developing the neurological condition Guillian-Barre syndrome (GBS)4 or Zika’s association with microcephaly in newborns.1,3

 In total 3,174 suspected Zika related microcephaly cases in Brazil have been confirmed with 38 associated infant deaths, Brazil has seen a 20-fold increase in microcephaly since the Zika outbreak.1 It should be noted that these cases have mainly been seen in rural Brazil, away from Rio. In total, it has been estimated that 1.5 million people have been infected with the Zika virus.5

What is interesting with these figures is roughly the same amount of people were infected with dengue fever, over the same time period, resulting in at least 800 deaths.5 While, microcephaly is not an avoidable complication for permanent residents of Brazil, for athletes and tourist travelling to Rio it can be avoided by not being pregnant or not falling pregnant within 56 days of returning.6 To me this suggests that the risk of dengue fever, yellow fever or another flavivirus should be of greater concern to any individual travelling to Brazil.

However, a letter written to the World Health Organisation (WHO) by 150 of the world’s top doctors, researchers and medical ethicists have demanded otherwise, suggesting the risk from Zika virus is significant enough that the Summer Olympic Games be postponed or moved.7 The letter also cites concerns over elevated levels of pollution and issues in the construction of venues and associated infrastructure. What is frustrating about these claims is that they have been made 2 months before the opening of the Games and I feel it was predictable that if you award a struggling nation like Brazil the Olympics you are going to be faced with certain challenges. Brazils construction industry has a notorious poor history8 and the pollution issues aren’t new.9 Didn’t we see this all before when Beijing were awarded the Olympics?

It is estimated that up to 1 million visitors including 200,000 from the United States are expected to travel to Rio to attend the games.10 There is no doubt that some of these visitors are likely to be infected with Zika but there are just as likely to be infected with the common cold if they stay at home and as long as they aren’t pregnant there are no major complications. Further, in February of this year the same number of people travelled to Rio to enjoy the Carnival11 and at no stage was there any public speculation about cancelling or postponing that event. Roughly, 6.4 million people travel to Brazil each year12 and while the Olympics is likely to increase this number it’s contribution to the spread of Zika is going to be limited.

The Zika virus itself is relatively mild and the biggest threat to public health is the associated neurological syndromes. However, Brazilian authorities in collaboration with the Organizing Committee for the Olympics and Paralympic Games have already outlined vector control measures in the Olympic vicinity.13 The United States continues with it’s extensive mosquito control activities, making the risk of Zika spread low. Furthermore, Dengue fever has long been an endemic in Brazil and has yet to spread to the United States.

I am confident that with education, proactive planning and preparedness, the effect of Zika virus on the Olympics and the world will be limited. It is my hope that the Rio games will be remember for it’s sporting moments rather than it’s offering of the Zika virus.


  1. Sampathkumar P. Sanchez J. Zika Virus in the Americas: A Review for Clinicians. Mayo Clinic Proc. 2016;91(4):514-521.
  2. Foy D. Kobylinski C. Chilson Foy L. et al. Probable nonvector-borne transmission of Zika virus. Emerg Infect Dis. 2011;17(5):880-882.
  3. Petersen L. Jamieson D. Powers A. Honein M. Zika Virus. The New England Journal of Medicine. 2016;372(16):1552-63.
  4. European Centre for Disease Prevention and Control. Zika virus epidemic in the Americas: potential association with microcephaly and Guillain-Barré syndrome. http://ecdc.europa.eu/en/publications/Publications/zika-virus-americas-association-withmicrocephaly-rapid-risk-assessment.pdf. Published December 10, 2015. Accessed March 28, 2016.
  5. Johnson R. and Jelmayer R. Brazil Grapples with spread of Zika Virus and Dengue Fever. The Wall Street Journal. [cited 2016 March 30]. Available from http://www.wsj.com/articles/brazil-grapples-with-spread-of-zika-virus-and-dengue-fever-1452032907
  6. Ministry of Health is advising women to delay pregnancy in light of Zika virus links to birth defects [press release]. Jamaica Ministry of Health website. http://moh.gov.jm/ministry-ofhealth- is-advising-women-to-delay-pregnancy-in-light-of zika-viruslinksto-birth-defects/. Published January 18, 2016. Accessed March 2, 2016.
  7. Open Letter to Dr. Margaret Chan, Director-General, WHO. [cited 2016 March 30]. Available from http://rioolympicslater.org.
  8. Salim C. Brazilian Construction industry; a contribution to improve information on fatal work accidents. Occup Environ Med. 2014;71
  9. Arnoud P and Wolthuis Y. Clean Urban delta Rio de Janeiro – an integrated agenda and approach. [cited 2016, March 30]. Available from http://kunststofkringloop.nl/wp-content/uploads/2014/05/CleanCityDeltaRio_eng_web_full.compressed.compressed.pdf
  10. Romero S and Ruiz R. Researchers weigh risks of Zika spreading at Rio Olympics. New York Times. [cited 2016, March 28]. Available from http://www.nytimes.com/2016/01/29/world/americas/brazil-zikario-olympics.html?_r.0.
  11. Withnal A. Rio Carnival 2014 in numbers: Brazil kicks off the greatest party on earth tomorrow – but where will the Samba parades take you? [cited 2016, March 28]. Available from http://www.theguardian.com/sustainable-business/2016/feb/01/funding-problems-hit-plan-clean-rios-polluted-waterways-olympics
  12. World bank. [cited 2016, March 28]. Available from http://data.worldbank.org/indicator/ST.INT.ARVL
  13. Fantz A. Darlington S. Olympics will inspect for water to help prevent Zika. Jan 24, 2016. CNN International Edition. http://edition.cnn.com/2016/01/24/world/olympics-rio zika/index.html (accessed Feb 3,2016).

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