Dengue is a mosquito-borne viral infection. According to World Health Organization (WHO), in recent decades global incidence of dengue has grown dramatically: About half of the world’s population is at risk. The infection causes flu-like illness, occasionally developing into a potentially lethal complication – severe dengue.
Dengue should be suspected when a high fever 104°F is accompanied by severe headache, pain behind the eyes, muscle and joint pains, nausea, vomiting, swollen glands or rash. Symptoms usually last for 2–7 days, after an incubation period of 4–10 days after the bite from an infected mosquito.
Severe dengue is a potentially deadly complication due to plasma leaking, fluid accumulation, respiratory distress, severe bleeding, or organ impairment. Warning signs occur 3–7 days after the first symptoms in conjunction with a decrease in temperature below 100°F and include: severe abdominal pain, persistent vomiting, rapid breathing, bleeding gums, fatigue, restlessness. The next 24–48 hours of the critical stage can be lethal. Proper medical care is needed to avoid complications and risk of death. There is no specific treatment or widely available vaccine for dengue.
According to World Health Organization, actual numbers of dengue cases are underreported, many of those are misclassified. One research indicates 390 million dengue infections per year, of which 96 million manifest clinically. Another study estimates that 3.9 billion people, in 128 countries are at risk of infection.
Before 1970, only 9 countries had experienced severe dengue epidemics. The disease is now endemic in more than 100 countries in the WHO regions of Africa, the Americas, the Eastern Mediterranean, South-East Asia and the Western Pacific. The America, South-East Asia and Western Pacific regions are the most seriously affected.
Cases across the Americas, South-East Asia and Western Pacific exceeded 1.2 million in 2008 and over 3.2 million in 2015 (based on official data submitted by Member States). Recently the number of reported cases has continued to increase. In 2015, 2.35 million cases of dengue were reported in the Americas alone, of which 10 200 cases were diagnosed as severe dengue causing 1181 deaths.
Not only is the number of cases increasing as the disease spreads to new areas, but explosive outbreaks are occurring. The threat of a possible outbreak of dengue fever now exists in Europe as local transmission was reported for the first time in France and Croatia in 2010 and imported cases were detected in 3 other European countries. In 2012, an outbreak of dengue on the Madeira islands of Portugal resulted in over 2 000 cases and imported cases were detected in mainland Portugal and 10 other countries in Europe. Among travellers returning from low- and middle-income countries, dengue is the second most diagnosed cause of fever after malaria.
In 2013, cases have occurred in Florida (United States of America) and Yunnan province of China. Dengue also continues to affect several South American countries, notably Costa Rica, Honduras and Mexico. In Asia, Singapore has reported an increase in cases after a lapse of several years and outbreaks have also been reported in Laos. In 2014, trends indicate increases in the number of cases in the People’s Republic of China, the Cook Islands, Fiji, Malaysia and Vanuatu, with Dengue Type 3 (DEN 3) affecting the Pacific Island countries after a lapse of over 10 years. Dengue was also reported in Japan after a lapse of over 70 years.
In 2015, Delhi, India, recorded its worst outbreak since 2006 with over 15 000 cases. The Island of Hawaii, United States of America, was affected by an outbreak with 181 cases reported in 2015 and ongoing transmission in 2016. The Pacific island countries of Fiji, Tonga and French Polynesia have continued to record cases.
The year 2016 was characterized by large dengue outbreaks worldwide. The Region of the Americas region reported more than 2.38 million cases in 2016, where Brazil alone contributed slightly less than 1.5 million cases, approximately 3 times higher than in 2014. 1032 dengue deaths were also reported in the region. The Western Pacific Region reported more than 375 000 suspected cases of dengue in 2016, of which the Philippines reported 176 411 and Malaysia 100 028 cases, representing a similar burden to the previous year for both countries. The Solomon Islands declared an outbreak with more than 7000 suspected. In the African Region, Burkina Faso reported a localized outbreak of dengue with 1061 probable cases.
According to the Pan American Health Organization, in 2018, the number of cases continues to grow. Annually hospitalization requires 500,000 people with severe dengue, the overwhelming majority of which are children. About 2.5% of them die.
The main vector of the dengue is Aedes aegypti. The virus is transmitted to humans through bites of infected females’ mosquitoes. After an incubation period of 4-10 days, an infected mosquito can transmit the virus throughout its life. Infected people are the main carriers of viruses, a source of viruses for uninfected mosquitoes.
Aedes aegypti live in urban conditions and breed mainly in artificial tanks. Unlike other mosquitoes Aedes aegypti eat in the afternoon.
Aedes albopictus, the second largest dengue vector in Asia, has spread to North America and more than 25 countries in the European region, largely as a result of international trade in old tires and the movement of goods. They can easily adapt to a new environment and therefore can survive in colder regions of Europe. The reasons for their spread are tolerance to temperatures below zero, hibernation and the ability to hide in microhabitats.
Currently, the only way to control/prevent the transmission of the dengue virus is vector control, individual protection and the use of effective anti-mosquito solutions.
Information Source: World Health Organization