Comment

www.thelancet.com/infection Published online May 17, 2014 http://dx.doi.org/10.1016/S1473-3099(10)70169-9 1

Football fans and fevers: dengue and the World Cup in BrazilBrazil—famous for its vibrant culture, wilderness, food, and beaches—is a major destination for travellers, including football lovers. Next month the Fédération Internationale de Football Association (FIFA) World Cup will bring more than a million visitors to the country.

Individuals travelling to new areas can bring pathogens with them, be exposed to infections they have not encountered previously, or return to their homes and infect others. World Cup spectators could risk acquiring viral hepatitis, infl uenza, chlamydia, typhoid, Escherischia coli, rabies, and others, among the many pathogens with which we share our environment, and sometimes our bodies.

As well as zoonotic, respiratory, enteric, and sexually transmitted infections, World Cup fans might be at risk for vector-borne diseases. Vectors have come and gone in Brazil. The malaria vector Anopheles gambiae sensu lato was introduced in 1930, but subsequently eliminated.1 Aedes aegypti, the main vector of dengue, was eliminated from Brazil in 1955, but returned in the 1970s.2 Risk can be modifi ed, and sometimes even eliminated, via vector control programmes. Dengue has been endemic in several Brazilian cities since 1986,2 but despite vector control programmes3 Brazil reported 1·4 million dengue cases in 2013. Last year, Hay4 suggested World Cup fans might be at risk for dengue.4 So how signifi cant is the risk of dengue during the FIFA World Cup?

In The Lancet Infectious Diseases, Rachel Lowe and colleagues5 present fi ndings derived from spatiotemporal modelling to forecast dengue risk at a fi ne spatial scale. The investigators project risk for microregions in Brazil and calculate risk levels that are useful for planning dengue control in the 12 cities where matches will be played.5 Their early warning system is based on a spatiotemporal Bayesian hierarchical model framework driven by climate and non-climate information. The work by Lowe and colleagues provides important information on risk in diff erent areas during the World Cup. We wonder how public health programmes and individual behaviour will modify this risk, and what the consequences will be for fans and for dengue epidemiology?

Risk for dengue infection is determined by the likelihood of A aegypti bites and number of infected bites.6,7 Informed World Cup fans will protect themselves

from A aegypti through choice of screened or air-conditioned accommodation, the use of insecticide, and appropriate light coloured and loose fi tting clothing. Risk for disease is determined by virus characteristics and by the immune response, age, sex, and comorbidities of the host.8 Some travellers might be infected, some of whom will get sick, but few, if any, will die.

Overseas visitors are unlikely to arrive with dengue viraemia, and the eff ect of the World Cup on dengue epidemiology in Brazil will be small, although increased domestic travel might have an eff ect. Travellers, particularly those attending matches in high-risk cities, identifi ed as Recife, Fortaleza, and Natal by Lowe and colleagues,5 might return home with dengue. Undoubtedly, Brazilian authorities, drawing on their vast public health experience, are instituting intensive vector control at stadiums, airports, and in high risk areas. These eff orts will greatly reduce risk. But many will come from temperate European countries without A aegypti, although the secondary vector Aedes albopictus is present in southern Europe.9 Those who return home unwell will seek treatment. Doctors must be aware of causes for febrile illness in World Cup spectators. Diagnosis of dengue is important for exclusion of other diagnoses, such as malaria. Symptomatic treatment will be suffi cient for most patients with dengue, apart from the few individuals, if any, who develop severe dengue.

We expect that few spectators will originate from tropical low-income and middle-income countries, and those who do will probably be wealthy, able to access good medical care, and likely to protect themselves from mosquito bites. Even in those who infect mosquitoes on their return, most will live in dengue endemic countries where the introduction of Brazilian dengue virus will make little diff erence to local epidemiology. Perhaps a few will return to tropical centres in wealthy countries where A aegypti is present but where the incidence of dengue is low. One such example is Cairns in far north Queensland, Australia,10 where dengue epidemics causally linked to, but geographically distant from, the World Cup in Brazil are possible.

The FIFA World Cup is a major sporting event. The results for dengue epidemiology, and on the football pitch, will be fascinating. We await both outcomes with interest.

Lancet Infect Dis 2014

Published OnlineMay 17, 2014http://dx.doi.org/10.1016/S1473-3099(14)70797-2

See Online//Articleshttp://dx.doi.org/10.1016/S1473-3099(14)70781-9

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Comment

2 www.thelancet.com/infection Published online May 17, 2014 http://dx.doi.org/S1473-3099(14)70797-2

*David Harley, Elvina ViennetNational Centre for Epidemiology and Population Health, The Australian National University, Canberra, ACT 0200, Australia David.Harley@anu.edu.au

We declare no competing interests.

1 Parmakelis A, Russello MA, Caccone A, et al. Historical analysis of a near disaster: Anopheles gambiae in Brazil. Am J Trop Med Hyg 2008; 78: 176–78.

2 Lourenço-de-Oliveira R, Vazeille M, de Filippis AMB, Failloux AB. Aedes aegypti in Brazil: genetically diff erentiated populations with high susceptibility to dengue and yellow fever viruses. Trans R Soc Trop Med Hyg 2004; 98: 43–54.

3 Maciel-de-Freitas R, Campos Avendanho F, Santos R, et al. Undesirable consequences of insecticide resistance following Aedes aegypti control activities due to a dengue outbreak. PLoS One 2014; 9: e92424.

4 Hay S. Football fever could be a dose of dengue. Nature 2013; 503: 439.

5 Lowe R, Barcellos C, Coelho C, et al. Dengue outlook for the World Cup in Brazil: an early warning model framework driven by real-time seasonal climate forecasts. Lancet Infect Dis 2014; published online May 17. http://dx.doi.org/10.1016/ S1473-3099(14)70781-9

6 Macdonald G. The epidemiology and control of malaria. London: Oxford University Press, 1957.

7 Gubler DJ. Dengue. In: Monath TP, ed. Epidemiology of arthropod-borne viral diseases. Boca Raton, FL: CRC Press, Inc, 1988: 223–60.

8 Halstead SB. Dengue. Lancet 2007; 370: 1644–52. 9 Waldock J, Chandra NL, Lelieveld J, et al. The role of environmental variables

on Aedes albopictus biology and chikungunya epidemiology. Pathog Glob Health 2013; 107: 224–41.

10 Bannister-Tyrrell M, Williams C, Ritchie SA, et al. Weather-driven variation in dengue activity in Australia examined using a process-based modeling approach. Am J Trop Med Hyg 2013; 88: 65–72.