Important fact
Dengue fever is a mosquito-borne virus infection.
Infections cause flu-like symptoms and sometimes develop into potentially fatal complications called severe dengue fever.
The incidence of dengue fever worldwide has increased significantly in recent decades. Today, about half of the world’s population is at risk of dengue fever.
Dengue fever occurs in tropical and subtropical climates around the world, mostly in urban and semi-urban areas.
There is no specific treatment for dengue/severe dengue fever, but early detection and appropriate care can reduce mortality to less than 1%.
Dengue fever is a mosquito-borne viral disease that has spread rapidly in all regions of WHO in recent years. The dengue virus is mainly transmitted by female Aedes aegypti and can also be transmitted by female Aedes albopictus. The mosquito also spreads Chikungunya, Yellow Fever, and Zika infection. Dengue fever is widely distributed in the tropics and is affected by rainfall, temperature and disorderly rapid urbanization. There are differences in the degree of risk faced by various regions.
Severe dengue fever was first discovered during the dengue epidemic in the Philippines and Thailand in the 1950s. Today, severe dengue affects most Asian and Latin American countries and has become a major cause of hospitalization and death among children and adults in these areas.
Dengue fever is caused by the virus of the Flaviviridae family, and four different but closely related viral serotypes cause dengue fever (DEN-1, DEN-2, DEN-3, and DEN-4). After infecting a virus and recovering it, it has lifelong immunity to the virus, but only a partial and transient cross-immunization of the other three viruses infected afterward. Subsequent infections (secondary infections) in other serotypes increase the risk of developing severe dengue.
Global burden of disease
The incidence of dengue fever has increased dramatically in the world in recent decades. The vast majority of cases are asymptomatic, so the actual number of dengue cases is more than the number reported, and many cases are misclassified. A study estimates that there are approximately 390 million cases of dengue infection each year (95% confidence interval 2.84-528 million), of which 96 million (0.67-1736 million) have clinical symptoms (of varying severity)1. Another study on the prevalence of dengue shows that 3.9 billion people in 128 countries worldwide are at risk of dengue virus infection.
Member States in the three WHO regions regularly report annual cases to the Secretariat. The number of reported cases increased from 2.2 million in 2010 to 3.34 million in 2016. Although the global burden of the disease is still uncertain, the increase in case reports in recent years is partly because countries have initiated activities to record all cases of dengue fever.
Other characteristics of the disease include its epidemiological model, including the high prevalence of multiple dengue virus serotypes in many countries and its astounding impact on human health and the global and national economy. The dengue virus is carried from one place to another by an infected traveler.
Distribution trend
Before 1970, only 9 countries had a prevalence of severe dengue fever, which is currently endemic in more than 100 countries in WHO, Africa, the Middle East, Southeast Asia, and the Western Pacific. The Americas, Southeast Asia, and the Western Pacific region are the most affected.
(According to official data submitted by the Member States to WHO) In 2008, there were more than 1.2 million cases of dengue fever in the Americas, Southeast Asia, and the Western Pacific Region, with more than 3.34 million cases in 2016. Recently, the number of reported cases has continued to increase. In 2015, only 2.35 million cases of dengue fever were reported in the Americas, of which 10,200 were diagnosed with severe dengue fever, resulting in 1,181 deaths.
As the disease spreads to new places, not only is the number of cases rising, but fulminant outbreaks are still occurring. There is now a threat of dengue outbreaks in Europe. In 2010, France and Croatia reported the first spread of dengue fever, and three other European countries have found imported cases. In 2012, the dengue epidemic in Madeira, Portugal, caused more than 2,000 people to become ill, and imported cases were found in the Portuguese mainland and 10 other European countries. Among travelers returning from low- and middle-income countries, dengue fever is the second most common cause of fever after malaria.
In 2015, Delhi, India, broke out the most serious epidemic since 2006, with more than 15,000 cases. The island of Hawaii in the United States was affected by the epidemic. In 2015, there were 181 cases reported and continued to spread in 2016. Pacific island countries Fiji, Tonga and French Polynesia continue to report cases.
A massive outbreak of dengue fever broke out in the world in 2016. In the Americas region, the number of cases reported in 2016 exceeded 2.38 million, and in Brazil alone, it reached nearly 1.5 million, about three times higher than in 2014. The region also reported 1032 deaths from dengue fever. In the Western Pacific Region, more than 375,000 suspected cases of dengue fever were reported in 2016, of which 176,411 were reported in the Philippines and 10,028 in Malaysia, and the burden of disease in these two countries was comparable to the same period of the previous year. Solomon Islands declared an outbreak of more than 7,000 suspected cases. In the African region, Burkina Faso reported a partial dengue outbreak and found 1061 possible cases.
In 2017, the number of dengue cases reported in the Americas decreased significantly, from 2,177,171 cases in 2016 to 584,263 cases in 2017, a reduction of 73%. In 2017, only the number of registered cases in Panama, Peru, and Aruba increased. Similarly, the number of severe dengue cases recorded in 2017 was also reduced by 53%. The number of cases of dengue fever after the outbreak of the Zika epidemic (after 2016) has declined, and the exact cause of this decline is still unknown.
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