Olympic Games Rio 2016 and the uninvited viruses: Potential consequences for Europe and North America
Juegos Olímpicos de Río 2016 y los virus no invitados: posibles consecuencias para Europa y América del Norte
In the Latin American tropics, we have witnessed the emergence of several pathogenic arboviruses in the last decade. These include Yellow Fever, West Nile virus, St. Louis encephalitis, Venezuelan equine encephalitis, Mayaro, Oropouche, Ilheus, and most recently, Chikungunya and Zika. Guillain-Barre syndrome (GBS), microcephaly and all the encephalitides, have been of concern to public health officials in Latin America since the arrival of emerging arboviruses. ¡Don't forget about dengue!
Between 2014 and 2015 we received two unexpected and uninvited viruses: Chikungunya and Zika. Chikungunya, an alphavirus, appeared abruptly in developing countries of the Americas, revealing that we were not prepared to face it. While we were still recovering from Chikungunya, Zika virus arrived, only compounding the insult. One cannot imagine the potential impact of the introduction of a hemorrhagic virus of the likes of Marburg or Ebola in Latin America. This scenario would be catastrophic.
The mosquito vectors in Latin America are already in place to disseminate emergent arboviruses like Chikungunya, Zika, Mayaro, and Oropouche. The arrival of the mosquitoes preceded the viruses by 3.5 billion years and they are standing by to transport the viruses across the continent. Besides Aedes aegypti, the vector of Dengue, Chikungunya, and Zika viruses, mosquitoes of the genus Culex are common in Latin America and ready to participate in the dissemination of new and old arboviruses in urban, rural and peridomestic areas.
Health authorities in Europe, the USA, and Canada are concerned about Zika virus infection and the return of their citizens and athletes following the 2016 Olympic Games. Yet they seem to be forgetting about Dengue, Chikungunya, Mayaro, and Oropouche viruses. Dengue is still the most common vector-borne disease in Latin American. The incidences of common arbovirus infections in Latin America are very high: approximately 173 cases/100000 inhabitants for dengue, 8 cases/100000 inhabitants for chikungunya, and 45 cases/100000 inhabitants for Zika. These epidemiologic data demonstrate very clearly that dengue should be considered a much greater concern than Zika and chikungunya (1).
The immunologic systems of Europeans and North Americans have no antibodies to tropical arboviruses, leaving them virtually defenseless against them. Most athletes and spectators will leave the competition and return home rapidly; thus, the spread of potentially viremic individuals could be wide and rapid. Humans infected with chikungunya virus appear to experience longer viremia than with Zika, dengue, and Mayaro viruses; thus, the greatest risk of disease spread may be from returning travelers infected with chikungunya virus. Furthermore, visitors will return to their countries in summer when high temperatures could facilitate the dissemination of the virus into autochthonous mosquito populations.
Female tourists and athletes in the beginning of pregnancy when they reach Brazil may be at risk of congenital disorders of their fetus if they are infected with Zika virus. However, many questions remain: Why is there still no animal model? Is it only a monoinfection or are other microorganisms involved in the infection? Are immune complexes involved in the pathogenesis?
The task for Brazilian authorities is to decrease the number of mosquito bites. This can be approached by using biological control (e.g., Wolbachia and Toxorhynchites) and by educating the community to remove containers with water where the mosquitoes breed. Use of repellents and oral complex vitamin B can also be useful in reducing bites. However, as was Ebola in the recent past, emerging viruses will always be of great concern. We are living in a period of biological transition brought on by many factors including modern transportation, worldwide trade, and climate change. We must adapt to this new world where infections are inevitable. Research on the eco-epidemiology of vectors leading to a greater understanding of the dynamics of tropical infectious diseases will be an important part of that adaptation process.
Why have we forgotten dengue? The annual economic impact of dengue in the Americas was estimated at US$ 2.6 billion in 2010. Ninety-nine percent of these costs are derived from the cases of Latin America and the Caribbean. The average cost per case in North America is yet 10x higher, estimated in 2010 at US$ 382. There is no doubt that associated costs in the current arbovirus emergence scenario (Dengue+Chikungunya+Zika) in Latin America, will further impoverish and collapse public health systems in developing countries (3).
Marco González T. M.Sc.
Salim Mattar V. Ph.D.
1. OPS/OMS. Number of Reported Cases of Dengue and Severe Dengue (SD) in the Americas, by Country: Figures for 2016 (to week noted by each country). Epidemiological Week / EW 16 (Updated April 29 2016). [En linea]. URL Available in: http://www.paho.org/hq/index.php?option=com_docman&task=doc_download&Itemid=&gid=34349&lang=es
2. Mattar S. Guillain-Barre syndrome, microcephaly and encephalitis, Is the recent incidence really due to Zika virus infection? Revista Laboratorio Actual 2016; 47:48-50
3. Shepard DS, Coudeville L, Halasa YA, Zambrano B, Dayan GH. Economic impact of dengue illness in the Americas. The American journal of tropical medicine and hygiene. 2011;84(2):200-7.