Viral diseases of hot climates

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What is it about ?

The conditions described in this patient guide are caused by viruses. These diseases occur almost exclusively in the tropics. Most viruses are transmitted to humans by mosquitoes, but some by mammals or from human to human.

Mosquito-borne viruses
  • Dengue (or red fever)
    • The dengue virus is found in Southeast Asia, the Caribbean, Central America, South America, and sporadically in Africa and Northern Australia.
    • This disease is currently on the rise in many tropical regions.
    • This virus is transmitted by the mosquito of the genus Aedes, which bites during the day.
    • Dengue fever causes severe symptoms and often lasts a long time.
  • Chikungunya
    • The chikungunya virus is found sporadically in large areas of Africa, Southeast Asia and India.
    • An epidemic has been underway in the Caribbean and Central America since 2014 and the virus has started to spread across the South American continent.
    • This virus is transmitted by the mosquito of the genus Aedes, which bites during the day.
  • Yellow fever
    • Fever is found only in sub-Saharan Africa (90% of cases) and South America.
    • This virus is transmitted by the Aedes aegypti mosquito, which bites during the day.
    • There is a vaccine against yellow fever, which is mandatory in countries where the disease is present.
  • Japanese encephalitis (inflammation of the brain)
    • This disease is most often found in India and Southeast Asia.
    • The virus is transmitted by Culex mosquitoes, which are active in the evening and at night.
    • Overall, the risk for travelers to the Far East is extremely low (less than one person traveling for 1 month in 1,000,000). Depending on the season, destination and travel conditions, the risk of contamination can reach up to 1 in 5,000.
  • Zika fever
    • The Zika virus is present in various countries in Asia, Africa, North America, Central America and South America.
    • This virus is transmitted by the mosquito of the genus Aedes, which bites during the day.
    • Zika virus can also be transmitted through sexual contact or mother-to-child transmission during pregnancy.
  • The malaria is another important tropical disease transmitted by mosquitoes. However, this disease is not caused by a virus, but by a parasite .
Virus transmitted from human to human

Contamination occurs first through contact between humans and animals (‘host’ of the virus), then directly from human to human.

  • Ebola
    • The Ebola virus is found mainly in Africa.
    • The hosts of this virus are wild animals, such as bats or monkeys.
    • Human-to-human transmission does not occur through the air, but through saliva, blood, urine, stool, vomit, sweat and sexual intercourse.
    • People who do not have a fever or symptoms are not contagious.

What is their frequency?

  • Dengue (or red fever)
    • The number of people infected with dengue is increasing globally due to population growth and urbanization. 45% of the world’s population live in areas where dengue fever is common.
    • Some 100 million cases of dengue are recorded each year.
    • The number of people who die from it is less than 1%.
  • Chikungunya
    • Each year, several cases of chikungunya are diagnosed among travelers in many European countries.
    • Deaths from chikungunya are rare and mainly affect very old people.
  • Yellow fever
    • The number of yellow fever cases is probably around 200,000 per year worldwide. In Belgium, the last case of yellow fever was recorded in 2002.
    • The death rate from the disease is around 5% and varies between 20 and 50% when jaundice develops.
  • Japanese encephalitis
    • Infections occur mainly between May and October, in rural areas and in expanding slums.
    • Each year, there are some 68,000 contaminations in the world.
    • In people who show signs of encephalitis , the risk of death is 30%. In 30% of cases, patients have sequelae.
  • Zika fever
    • Latin America was affected by a very large epidemic of Zika fever in 2015 and 2016. This epidemic is practically over in 2019, so that the risk of contamination has dropped sharply.
    • About 6% of children of mothers infected with Zika virus during pregnancy develop birth defects.
    • The death rate is very low.
  • Ebola
    • In 2014, a large Ebola epidemic raged in several West African countries. Tens of thousands of cases have been identified and international intervention has been necessary to bring the situation under control. A few sporadic cases have also spread to Western countries.
    • About 50% of those infected with Ebola die

How to recognize them?

  • Dengue (or red fever)
    • This infection is characterized by very sudden onset, accompanied by fever , severe headache and pain in the joints , pain behind the eyes, and pain in the muscles . A dry cough is sometimes present.
    • Symptoms appear 4 to 10 days after infection. Often, the fever goes away after 3 to 4 days, but reappears a few days later, along with a mottled rash .
    • Symptoms disappear within 2 weeks, but there can be a difficult period of recovery, which can last for several weeks and is accompanied by complaints such as fatigue , depression and muscle pain .
    • A potentially fatal and extremely rare form of the disease is characterized by severe stomach pain , vomiting and bleeding.
  • Chikungunya
    • Chikungunya usually begins 3 to 7 days after infection and has a very sudden onset, characterized by high fever , flu- like symptoms and severe pain in the joints of the ankles, wrists and / or fingers. The infected person may have difficulty walking. Otherwise, there is sometimes swelling of the hands and / or feet, headaches , a rash or light bleeding (gums).
    • In most cases, symptoms go away after a week, but in a number of people, joint pain can persist for weeks or even months.
  • Yellow fever
    • Yellow fever very often has a mild course: it sometimes even happens that the disease goes unnoticed or looks like a mild flu .
    • Sometimes the symptoms are more severe and may include jaundice and bleeding (including spontaneous bruising (bruising) ).
    • Symptoms appear 3 to 6 days after infection.
  • Japanese encephalitis
  • Zika fever
    • Symptoms of Zika virus infection are mild; the disease sometimes goes unnoticed.
    • A rash with itching is common. Sometimes it is also about fever , joint pain , eye inflammation, headache and fatigue .
    • Symptoms last from a few days to a week. Often the doctor is not even consulted.
    • In rare cases, neurological complications are possible, such as Guillain-Barré syndrome .
    • The Zika virus is especially dangerous for the fetus of an infected mother. Zika virus infection can cause miscarriage or birth defects, such as an undersized skull (microcephaly), vision or hearing problems , growth retardation, mental retardation, or epilepsy .
  • Ebola
    • Ebola is characterized by a fever associated with an unexplained tendency to bleed from the skin and internal organs. It is often about vomiting and diarrhea , headache , eye inflammation and muscle pain .
    • The first symptoms appear on average 7 to 10 days after contamination, but at most after 21 days.

How is the diagnosis made?

The doctor will suspect one of these infections if there is fever or other symptoms after traveling to a contaminated area. The diagnosis can only be made with a specific blood test, which detects antibodies against the viruses in question.

What can you do ?

If you become ill after traveling to a tropical region, see your doctor. Otherwise, it is advisable to apply the following measures in order to avoid contamination  :

Vaccination

There are vaccines against yellow fever and Japanese encephalitis.

  • Yellow fever
    • In some countries, the vaccine against yellow fever is compulsory. Many countries also require a booster vaccination every 10 years.
    • The yellow fever vaccine can only be administered at an approved provincial health center or at the Institute of Tropical Medicine (Antwerp).
    • The vaccine contains live attenuated viruses and cannot be given to pregnant women or to people with weakened immune systems. Great caution should also be taken in children under 9 months of age and in people over 60 years of age.
  • Japanese encephalitis
    • Vaccination against Japanese encephalitis is not recommended for all tourists.
    • The vaccine is especially useful for travelers or workers who stay at least 3 to 4 weeks, between May and October, in a high risk area.

In addition to the above vaccinations, other vaccines are strongly recommended before going on a trip:

For example, visit the Institute of Tropical Medicine (IMT) website to find out which vaccines are recommended for your specific destination, or contact your doctor to discuss them.

Mosquito protection

Some mosquitoes bite mostly during the day, others mostly in the evening and at night. Here are some important tips for avoiding mosquito bites  :

  • Wear clothes that cover your arms, legs, and feet.
  • Apply a repellent to any parts of the body that are exposed. Preferably use a product containing DEET at a concentration between 30 and 50%.
    • In pregnant women and children, a concentration of 20 to 30% is rather recommended.
    • Apply the product every 4 to 6 hours on average.
    • Avoid contact with mucous membranes (eyes, mouth), wounds or eczema lesions .
    • If you also use sunscreen, apply sunscreen first, then DEET. Use a sunscreen with a high protection factor (30 or more), as DEET decreases the effectiveness of the sunscreen.
  • Wear clothing impregnated with insecticide (permethrin) if necessary.
  • Sleep under a mosquito net impregnated with insecticide (permethrin or deltamethrin). You will easily find it in shops.
  • For a mosquito-free bedroom, eg install mosquito nets on windows and vents.
Protection against Zika virus
  • Pregnant women are advised not to travel to areas where the Zika virus is actively spreading. These are more precisely the countries displayed in red on this map .
  • If you are going on a trip to a country where the Zika virus is present (in purple on this same map) make sure you protect yourself against mosquitoes during the day and use condoms. Before you leave, discuss the risk of contamination with your doctor.
  • Women returning from epidemic areas or recovering from Zika virus infection should postpone any attempted pregnancy for 8 weeks.
  • Men returning from epidemic areas should:
    • refrain from having unprotected sex for 8 weeks if they have not shown symptoms that suggest Zika virus infection;
    • refrain from having unprotected sex for 6 months if they have contracted the disease.

What can your doctor do?

There is no treatment for these viral infections. Most often they heal on their own.

  • In case of dengue fever (red fever), the use of aspirin or anti-inflammatory drugs such as ibuprofen is not recommended. Preferably use paracetamol.
  • Serious complications such as spontaneous bleeding require hospitalization.
  • People infected with a viral disease, who are contagious, are subject to strict isolation.

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