Epidemiology of dengue and chikungunya viruses and their potential impact on the blood supply

Dengue and chikungunya, transmitted by the Aedes mosquitoes, have caught worldwide attention because of increase in the frequency of major epidemics in recent years. Though transmitted by the same vectors, they are caused by different viruses (DENV and CHIKV) that belong to the genus Flavivirus and Alphavirus, respectively. There has been a worldwide resurgence of dengue in the last few decades. Today, it is estimated that it affects at least 50–100 million people every year. With more than 100 countries, between the 10°C isothermal lines, being endemic, 2·5 billion people are at risk of infection. Facilitated by rapid urbanization and increased travel, the disease continues to make its geographical spread, and the number of cases continues to rise across the world. Chikungunya outbreaks have been reported in Asia and Africa. Major epidemics appear and disappear cyclically, usually with an inter‐epidemic period of 7–20 years. However, its recent unprecedented explosive outbreaks since 2005, revealed an altered epidemiology. Millions of cases have been reported as the disease sweeps across the islands in the Indian Ocean, followed by countries in South Asia and South East Asia. An outbreak in Italy in 2007 demonstrated the threat of the tropical disease to temperate countries. These two Aedes‐borne diseases have also impacted travellers significantly, with numerous reports of imported cases in countries with no transmission. In both diseases, viruses have been detected prior to the onset of symptoms, and asymptomatic cases have also been reported. As a result, under‐ and delayed diagnoses have led to dengue transmission through organ transplant and blood transfusion. The potential impact of the epidemiology of the two diseases on the safety of blood and organ donation will be discussed.