Dengue World Cup
Ginny - Now, I don't know if you're a football fan. I must admit, I'm not, but even I can't escape talk of the upcoming World Cup in Brazil. Conditions there are predicted to reach fever pitch for more than just the matches though because a new disease forecasting system is predicting epidemics of dengue fever. Dengue is a mosquito-borne viral illness that causes high fevers and severe bone and joint pains. In some cases, it can even be life-threatening. Dengue is endemic in Brazil and it follows a seasonal pattern linked to the weather with conditions that favour mosquito breeding, making an epidemic more likely. Now Rachel Lowe and her colleagues at the Catalan Institute of Climate Sciences in Barcelona have designed a computer model that can forecast 3 months ahead the likelihood of dengue epidemics in a given geography. Rachel gave Chris Smith the details...
Rachel - We've put together an early warning system for dengue fever in brazil which brings together many different risk factors for dengue and climate information. What we then do is use forecasts of the climate information to try and predict where it may be more likely to have dengue epidemics.
Chris - This is of course relevant because pretty soon, FIFA estimate more than a million people are expected to descend on Brazil for of course the World Cup.
Rachel - Exactly. So in this case, we got together with the climate services in Brazil and the Ministry of Health, putting together the latest data on the dengue cases and the temperature and precipitation for the month preceding the games to try and say when and where there might be more likely to be dengue outbreaks or not.
Chris - So, how have you used the information we have on what's happened in the past in Brazil to try to make these predictions about where there'll be activity around the country?
Rachel - We took the dengue cases over the last 14 years for 553 regions of Brazil, combined this with information on climates and also non-climatic factors. We combine this into a model and then we used severity thresholds that are used by the Ministry of Health to work out the chance of dengue cases exceeding medium and high levels. We looked at the performance of the early warning system on past data and using this, we devised optimum trigger thresholds to indicate whether low, medium or high warning should be issued for the 12 host venues.
Chris - I see. So, by using data of what has happened in the past and how those weather patterns and so on coincide with the sorts of numbers you get for dengue, you can then have a sort of system that will enable you to predict, if the same climate patterns come along this year, this is where we would expect to have activity of the following amounts in these different geographies.
Rachel - Exactly. The model takes into account differences in dengue throughout the year and also, in different ecological zones.
Chris - When would the dengue season normally be in Brazil?
Rachel - Mainly between January and May.
Chris - So, by the time most of the people would be visiting, we would expect the disease activity to be waning.
Rachel - Yeah, we'd expect it to be exactly on the decrease.
Chris - But what does your model say about the different areas where the different parts of the World Cup are going to be played?
Rachel - In the 3 north-eastern cities of Natal, Fortaleza and Recife, there is an increased chance of a dengue outbreak. There are medium levels in some of the other stadiums such as Rio de Janeiro, Salvador and Manaus, and in the southern cities, the risk is most likely to be low.
Chris - Can you just tell us, what does a high risk mean?
Rachel - The way we defined it was a probability of dengue cases within the micro-region exceeding 300 cases per 100,000 inhabitants.
Chris - What's the likelihood of those 3 areas - Natal, Fortaleza and Recife are going to have those sorts of numbers?
Rachel - The probability of exceeding that threshold in Natal is 48%, in Fortaleza 46% and in Recife 19%.
Chris - So that's really a reasonable chance of high dengue activity in 3 areas which do overlap with where games are scheduled to be played.
Rachel - Yes, so the idea of this model is, it's capable of issuing warnings 3 months in advance. That can be incorporated into the decision making of the local authorities and the dengue control people to help concentrate intervention activities in those areas.
Chris - Would that mean for instance spraying for mosquitoes, giving people advice, telling people to wear mosquito repellents for example.
Rachel - Yes and the dengue control teams have been going house to house, checking for potential mosquito breeding sites, destroying them.
Chris - What do the Brazilian authorities say about this? I presume you've shared your findings with them.
Rachel - Yes. We actually are, our Co-authors included scientists from the Ministry of Health. They've been very supportive of the study. They provided inputs about how to use these results in the health policy way and they provided us with the latest data in order to produce the forecast.
Chris - But more importantly, have they also now formulated a strategy for the World Cup based upon your predictions which suggests that there are 3 hotspots which fans maybe need to be aware of and which authorities need to act on.
Rachel - The National Dengue Control Programme are working very hard in all the cities ahead of the World Cup to make sure that the dengue risk will be at the minimum.
Ginny - Dr. Rachel Lowe from the Catalan Institute of Climate Sciences in Barcelona.