Dengue Fever:
After Malaria, Dengue is the most common and serious mosquito-borne infection affecting travellers and may become severe and life threatening. It is an Arbovirus (any virus transmitted by arthropod vectors) transmitted by the mosquito Aedes Aegypti (The same mosquito that transmits Yellow Fever, Zika and Chikungunya diseases).
Dengue is endemic in South-East Asia, the Indian sub-continent, the Pacific region as far as Queensland in Australia, the Caribbean Islands, north and eastern parts of Central and South America, to a lesser extent the Middle East and sporadically in Africa. Outbreaks could be common especially after the rainy seasons when mosquitoes breed more actively.
Global warming is spreading the mosquito vector to more temperate regions and higher altitudes and epidemics are widespread in Central and South Americaand also Asia. There has been a 30 fold increase in incidence globally over the last 50 years. It is estimated that 3.9 billion people in 128 countries are at risk. Many cases are underreported but it is estimated that 390million infections occur annually of which 96 million are symptomatic. The mosquito bites predominantly during the day so protective measures should apply to daytime and nighttimes.
Tourists staying for longer periods especially living in rural areas with poorly screened accommodation are at high risk. (Though most infections occur in urban and semi-urban areas)The Dengue viruses (DENV), a flavivirus is the cause of infection. The incubation period is 4 to 10 days after which a sudden onset of fever (>38.5®C), headache, myalgia and arthralgia (Muscle pain & Joint pain) may occur and a fine maculopapular rash may develop shortly after (3-5 days). Nausea, vomiting, diarrhoea, meningism and enlarged lymph nodes may occur. The illness usually resolves within a few days and serious complications are uncommon. Most infections are asymptomatic or present with a mild febrile illness (3 to 7 days) and resolve in phase 1.
In the critical phase, Dengue Haemorrhagic Fever, more common in children is a haemorrhagic form that can present with shock and can be fatal. Persistent vomiting, increasing abdominal pain, tender liver, mucosal bleeding lethargy and restlessness are signs to look for. Incidence is around 2% with around 1-2% of those cases being fatal in some studies.
Treatment is symptomatic and supportive, but hospital care is indicated in severe cases which may include blood transfusions. Severe fatigue may last for months. Avoiding mosquito bites is essential using appropriate clothing, repellents and adequate mosquito nets. Air-conditioned environments help also. There is no known treatment or cure for the virus, but a vaccine is available. The vaccine is still on trial in some countries, but Mexico, Costa Rica, Brazil and the Philippines are the first countries to authorise the use of Dengvaxia.
In the UK, Dengue is the second most common cause of febrile illness in returning travellers and the number of cases in travellers continues to increase. Of interest to note is that DENV has 4 distinct serotypes (DENV 1 to 4) infection with one of the serotypes induces lifelong protective immunity to that infecting serotype and immunity to other serotypes, but this is short lived for on average 2 years. If you are infected with a different serotype after this cross-protecting immunity has waned, you are at increased risk of developing a severe form of dengue.
Rabies:
Rabies is deadly disease which causes most certain death froman acute encephalitis caused by the rabies virus. Only one case report of recovery from clinical rabies exists in the world literature and it is believed that the person received some form of Post-exposure Prophylaxis (PEP) before the onset of illness. Other stories you may have heard that survived (about 4 in all) hadsome previous (not complete) vaccinations against the virus and all had some neurologic serious sequelae.
My advice is that, if you or any family member is at risk for Rabies locally or travelling, take you complete preventive 3 dose shots and know you have taken some form of “life insurance” (Children are more vulnerable than adults because they cannotcomprehend the risk of animals, are less able to defend themselves from an animal attack and may not report a potential exposure). It is virtual 100% preventable if proper vaccination and care is taken.
Rabies can affect many animals, but the dog, fox, cat and vampire bat are those most likely to come in contact with humans? Be careful of bites, scratches, tiny nibbles andlicks/saliva (especially if you have an exposed wound) of animals.
All rabies treatment should be initiated as soon as possible. Cases of rabies have been reported as much as six years following a rabid animal bite, so management must be done even beyond six years as if the bite has just occurred. In the immediate care of bites, saliva should be thoroughly washed off with soap and water and the wound irrigated with Iodine solution or alcohol. This is very effective in removing the virus from the bite site. Do not suture the wound. If you have not been immunised before the bite, you must seek medical attention within 24hrs.
Immunoglobulin (gives immediate protection) is given immediately and a full course of 5 doses of modern day vaccine (which is not immunoglobulin) should be given over 28days.It is advisable to immunise yourself and family, especially if you think you are at risk locally or when travelling. 3 doses of vaccine are given over a period of 3 -4 weeks, and if at any time you are bitten by a suspected rabid animal, seek medical advice and you will most likely need to take only 2 more booster doses at the maximum for a total of 5 doses, immunoglobulin should not be necessary. Immunoglobulin is often not available or difficult to obtain in many developing countries so preventive vaccination may be advised.
In a WHO study in 2004, the annual death from rabies is estimated to be 55,000 mainly in rural areas of Asia and Africa. It is spread mainly by bats in South and North America. Those at high risk include cave explorers, cyclists/runners, zoologists, botanists, volunteers in animal sanctuaries and veterinary surgeons.
Every year, more than 15 million people worldwide receive a post-bite vaccination. This is estimated to prevent hundreds of thousands of rabies deaths annually.
Dr Ade Alakija
Q-Life Advisory Services
