A recent outbreak of dengue in Madeira has resulted in a flurry of articles and reports. According to the European Centre for Disease Prevention and Control (ECDC), Europe has not experienced a sustained transmission of dengue fever since the 1920s. As of Dec. 9, there was an estimated 2050 cases reported.

Dengue Fever

Mosquitoes infected with one of four dengue viruses spread dengue. The Aedes aegypti mosquito is the main vector, although there’s been at least one outbreak with Aedes albopictus as the transmitter. Mosquitoes, which become infected after biting individuals infected with dengue, can spread the virus after about a week. Dengue is typically present in Asia, the Pacific, the Caribbean, the Americas and Africa.

Symptoms of dengue fever often include high fever, severe headache, severe pain behind the eyes, muscle, joint and bone pain, rash, and mild bleeding. However the degree of illness varies.

Countries with reported cases

Travelers can introduce dengue to other regions if infected while visiting areas where dengue commonly exists. ECDC reports that “a small number of visiting tourists [to Madeira] have been diagnosed with dengue infection after developing symptoms back in their home countries. The United Kingdom has reported six cases imported from Madeira, France and Germany two cases each, and Sweden one case. … In addition, eight cases were diagnosed after returning to mainland Portugal.” 


A visualization of alert volume on HealthMap shows a significant increase in the number of online articles and reports related to dengue fever in the aforementioned regions. HealthMap utilizes informal sources for aggregating and organizing information for outbreak monitoring and surveillance. The alerts published on HealthMap.org are categorized as “breaking” or “warning,” indicating real-time relevance on an ongoing outbreak or updates on case counts. The graphs displayed depict number of alerts on dengue for each country aggregated by year.  Similar to Internet search query volume, alert volume from HealthMap has been used in the past to estimate disease activity in a region.  However, in this case, an increase in alert volume might be due solely to media frenzy and might not necessary be representative of an increase in dengue incidence in these regions. It is interesting to note the increase in reports on dengue fever across six of the seven countries with a significant increase in 2012 for most. The ECDC expects more dengue cases as “peak mosquito breeding period, including the dengue vector Aedes aegypti will continue until the beginning of next year and coincides with a peak in the number of visitors” to Madeira.


Dengue Prevention and Treatment

No particular medication or vaccine exists for treatment or prevention of dengue. However, individuals who live where there are Aedes aegypti mosquitoes can take preventive measures to minimize the spread of dengue. These measures include reducing habitats where mosquitoes lay eggs such as standing water, using bed nets, door screens and applying mosquito repellents.

Photo credit: Elaine Nsoesie




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