Dengue fever is endemic in most tropical and sub-tropical countries, which is also a popular tourist destination.
Dengue fever has been designated as a major international public health problem by the World Health Organization (WHO).
Tourists not only have a significant risk of dengue fever but they also contribute to its spread to non-endemic areas. In fact, for travelers returning from Southeast Asia, dengue fever is now more often the cause of fever than malaria.
Tourists infected with dengue who return to countries where the vector exists can place the local population at risk of further disease transmission with subsequent autochthonous infection cycles.
The incidence of actual dengue among travelers can be underestimated because of the variability in reporting requirements in various countries and a low diagnosis due to clinical presentation of non-specific diseases. Risk factors for developing dengue fever include length of stay, travel season and epidemic activity at the destination.
Any pre-trip advice about the risk of developing dengue infection must consider these factors.
Women infected with dengue who return home can place the local population at risk of spreading the disease, further where mosquito vectors, Aedes aegypti or A. albopictus, each primary and secondary vector, are each present.
The increasing global spread of vectors means that many non-endemic countries have mosquito populations capable of spreading dengue viruses introduced by tourists who have returned to travel
Populations in non-endemic countries may also be at risk of developing dengue fever in other ways. Although it only represents a small proportion of dengue fever cases, this disease can also spread through a mechanism that does not involve mosquitoes as a vector, such as transmission through hospitals especially through blood transfusions.
Transmission of needle fever or mucocutaneous exposure to blood has been reported in health care workers in non-endemic countries. However, blood products are not screened for dengue, and further studies are needed to assess the risk of infected blood for transmission
Risk factors for obtaining dengue fever include length of stay, travel season and epidemic activity at the destination. Although reports of cases of dengue fever increase during the rainy season, this varies according to country and even between regions within the country. Because it is difficult to correlate rainfall accurately with the incidence of dengue fever.
Most cases of travel-related dengue, such as in endemic populations, show no symptoms or symptoms at a minimum. However, when symptoms develop, because of their non-specific nature, they are often misdiagnosed as a number of other febrile illnesses such as chikungunya, malaria, typhoid fever and rickets infection. Furthermore, because laboratory-based diagnosis is often not available at the time of treatment, the diagnosis often must be made solely at clinical presentation.
However, in patients with threatening but potentially treatable febrile illnesses such as typhoid fever and malaria it must always be issued first. Also, given the short incubation period, the diagnosis of dengue is not possible if the initial presentation is more than 2 weeks after returning from an endemic country.
Dengue fever is thought to occur as a continuous spectrum of severity. The current WHO case definition for the diagnosis of dengue is separated into patients with severe and non-severe dengue, with a large group of dengue sufferers who are not severely divided. Surveillance reports from the European Network on Imported Infectious Disease Control (TropNetEurop) show that European travelers present with a variety of symptoms, but the majority with confirmed diagnoses or possible dengue fever are presented with uncomplicated dengue fever with typical symptoms of fever, headache, fatigue and musculoskeletal pain
The Center for Travel and Tropical Medicine (CRM) in Berlin said it was notified of 45,700 cases of dengue fever in 2018, in which at least 45 people died from the disease. The only good news here is that the numbers have dropped since 2017, when at least 395 died of dengue hemorrhagic fever from 185,195 infections.
Dengue fever usually doesn’t turn off when you first get it. The first infection will give you flu-like symptoms that begin two to ten days after you are bitten. Typical symptoms include high temperature, headaches, aching limbs, back pain and a low rash. Pain and fever tend to disappear quite quickly, but may feel tired for several weeks.
Dengue fever is very dangerous after the second or third infection. This is when more severe symptoms, such as internal bleeding and the so-called dengue shock syndrome, can occur.
However, certain combinations of clinical features and laboratory abnormalities may be better able to predict dengue fever in tourists. In a study of Australian tourists who returned to illness, the diagnosis of dengue was more likely if a combination of fever and leukopenia, fever and rash, rash and leukopenia. Because of the increasing prevalence and non-specific symptoms of dengue fever, it is important for health professionals around the world to recognize its clinical features.
Dengue seems to occur less frequently in travelers than in populations in endemic countries. In endemic areas, about 6% of symptomatic dengue cases develop into DHF. In comparison, intensive supervision of travelers conducted in TropNetEurop revealed that, out of 219 infected dengue tourism, 0 · 9% met WHO 1997 criteria for DHF, although 11% of patients experienced severe clinical manifestations.
Dengue affects both sexes equally, unlike malaria, which more often affects male tourists than female tourists. The duration of the trip is slightly shorter for tourists with dengue who visit as tourists than for those who suffer from malaria, most of whom visit friends or relatives.
According to the WHO case definition, severe dengue fever, which includes symptoms of dengue hemorrhagic fever (DHF), is characterized by plasma leakage, bleeding and severe organ damage. Severe dengue seems to be less common in tourists than in populations in endemic countries.
According to CRM, travelers are usually not infected more than once during the holidays. But you may still have to see a health installation if you show signs of flu just in case.
Another factor that contributes to the low incidence of dengue in tourists is that most are adults who are reported to have a lower risk of dengue than children.
Children represent a significant proportion of people who travel, accounting for 7% (1 · 9 million) of tourists. Severe dengue fever in children poses a significant burden on endemic countries such as Thailand, which has an annual average burden caused by dengue fever.
Children have a higher risk than adults who suffer from severe dengue fever, the main cause of morbidity and mortality in the age group. The risk of death from secondary infections is almost 15 times higher than adults. It is believed that 10% of children with secondary infections continue to develop.
There are currently no licensed dengue vaccines, and measures such as vector control have proven to be inadequate in reducing the incidence of dengue fever. Therefore, with only the support of dengue fever support available, protection against dengue is limited to avoiding mosquito bites by using insect repellents, protective clothing and insecticides.
Avoiding rubbish and containers with stagnant water is also recommended. Protection measures need to be taken during the day because this is when mosquitoes bite, with only the effectiveness of limited nighttime actions such as an insecticide-treated mosquito net. Therefore an effective and economical vaccine against dengue will be a major advance in controlling disease.
Given the high incidence of this disease in tourists, vaccines for them can also be indicated, provided they are safe, comfortable to manage and affordable. The most distant vaccine candidate in development is the chimeric vaccine by Sanofi Pasteur. With the lead vaccine candidate showing encouraging results in the final clinical trial, the prospect of introducing vaccines against the four serotypes of dengue fever into the national immunization program of endemic countries is very promising.
The incidence of dengue fever in international travelers, including children, is increasing. In addition, travelers contribute to the geographical spread of dengue fever and its introduction to previously uninfected areas.
The increasing number of dengue fever cases reported worldwide, and identification of dengue infections acquired locally in non-endemic areas, emphasizes the need to monitor tourists returning from endemic areas. Because the incidence of dengue shows the seasons and variations according to the purpose of the trip, advice before the trip should consider epidemic activity, seasonal patterns and travel destinations.