As we’ve seen often over the past few decades, Dengue fever continues its geographic expansion, spurred on both by climate change and the ease of human travel around the globe.
All it takes is for a traveler to be bitten by an infected mosquito in one region, and then travel to another region while viremic where suitable mosquito hosts can be encountered, to import the virus into a new place.
The explosive growth of Dengue around the world is well illustrated by the following graph from the World Health Organization. In just over 20 years (1980-2000) the number of countries reporting Dengue Fever cases doubled.
What this graph doesn’t indicate is another doubling of dengue cases over the past 5 years.
In 2009, it was Key West in South Florida that saw the introduction, likely through tourism, of the virus (see MMWR: Dengue Fever In Key West).
For the first time in their history – and In just over 6 weeks time - more than 1,357 cases of Dengue Fever have been reported in the Autonomous region of Madeira, an island with just over a quarter of a million residents, located 1000 km west of Portugal.
With more than a million visitors a year, Madeira is a popular vacation spot, and that adds greatly to the local economy. But that also increases the risk of importing the virus via an infected traveler.
The ECDC has updated their earlier Risk Assessment (issued October 10th) today. While they acknowledge that dengue transmission is likely to continue at least through the end of the year, they do not recommend trade or travel restriction beyond the disinfestations currently being implemented.
20 Nov 2012
The Autonomous Region of Madeira constituted the first known occurrence of locally transmitted dengue infection on the island on 3 October 2012 when the Public Health Authority of Portugal reported two cases of dengue infection in residents. These infections in patients residing in Madeira mark the first sustained transmission of dengue in the European Union since the 1920s.
Local transmission of dengue infection has been now established for several weeks on Madeira and as of 11 November 2012, the Portuguese Ministry of Health reported 1 357 cases of dengue infection from the public health sector in Madeira. 669 of these cases were laboratory confirmed, 688 probable cases. Since the beginning of the outbreak, 89 patients were hospitalised and five currently remain in hospital. So far, 25 patients have been diagnosed with dengue after returning from the island: cases were reported from mainland Portugal (nine), the UK (six), Germany (seven), Sweden (one) and France (two).
In the meantime, Portuguese and regional health authorities have been implementing control measures to limit extension of the outbreak to reduce the risk of sustained transmission locally and that of exportation of infected vectors from the island. In addition, ECDC provided technical assistance to the health authorities in Madeira in their efforts to control the outbreak by deploying an expert mission from 22 October until 16 November. Following this visit, ECDC updated its initial rapid risk assessment on the situation. The updated assessment reconfirms that the current epidemiological situation does not imply any trade or travel restriction beyond the disinfestations implemented on the island at present.
However, residents as well as tourists are strongly advised to take individual protective measures – like using repellents – to avoid mosquito bites. Dengue is transmitted by a daytime mosquito (Aedes aegypti) and thus protective measures should be applied throughout the whole day.
The latest data indicate that the outbreak is still on-going and its exact development cannot be anticipated at this point of time. With tourists visiting Madeira, continued import of dengue cases from the island to other EU countries is to be expected until the mosquito population is decreased and transmission interrupted.
Anyone who develops a fever or flu-like symptoms (with severe headache, retro-orbital pain, myalgia, arthralgia and maculo-papular rash) within two weeks of returning from a trip to Madeira should seek medical advice.