Dengue Fever - Update
- Rachel Smith
- Aug 1, 2024
- 4 min read
The global incidence of dengue fever has increased noticeably over the last 20 years and now poses a substantial public health challenge. Transmission is cyclical and large outbreaks are expected every 3-4 years, but since the beginning of 2023 there has been an unexpected rise in cases and deaths in countries with an established risk (endemic), as well as evidence of dengue spreading into areas previously thought to be dengue-free.
In the first 4 months of 2024, over 5 million cases and over 2,000 deaths were reported worldwide. Increased cases were reported in known dengue regions including Asia, Central and South America and across the Caribbean.
Dengue is not endemic in Europe, but with favourable environmental conditions, dengue carrying mosquitoes can cause local spread of the disease. In 2023, locally acquired cases were reported in France, Italy and Spain; areas not normally associated with dengue and where testing isn’t routine. There has also recently been a case reported in Florida. The World Health Organisation has assessed the current risk to be high globally.
So what do we know about Dengue? Dengue is a viral infection, with four different types, spread by infected mosquitoes, usually the Aedes aegypti (thought to be driving many current outbreaks) and Aedes albopictus (which has capacity to hibernate in winter) varieties. It can’t be spread from person to person.
The mosquitoes bite during the day, usually early morning or in the early evening just before dusk. They thrive in warm humid environments so climate change and a rise in temperature, more extreme wet weather, high rainfall and humidity is helping to extend their habitat range. They're often found near still water in built-up areas, such as in wells, water storage tanks, discarded bottle tops, air conditioner trays or in old car tyres.
Other contributory factors to this sudden risk includes the consequences of the El Nino phenomena in 2023 (predicted again in 2026) and fragile health systems resulting from the COVID-19 pandemic. Weakness in surveillance systems have led to delays in reporting and response, including missed identification of symptoms, contributing to increased severe dengue outcomes.
While we’re not at great risk in the UK, dengue is widespread in many parts of the world such as Southeast Asia, the Caribbean, the Indian subcontinent, South and Central America, Africa, the Pacific Islands and Australia. Risk is increasing in the Mediterranean and other regions. A vaccine is available from private travel clinics, but it takes 3 months to administer the two doses, meaning that advanced planning is needed. It is normally recommended only for those travelling to endemic regions, or who have had Dengue before. So it’s important to take steps to prevent infection in the first place.
Only one in four cases are symptomatic and some infections may produce mild, flu-like symptoms. Dengue normally presents as a mild infection that develops suddenly, around 5-8 days after being infected, and passes in around a week with no lasting damage other than maybe feeling tired and a bit unwell for a few weeks. So it can normally be managed without needing hospital treatment by managing the symptoms.
Occasionally it can become life threatening and in rare cases (5%), severe dengue can develop after the initial symptoms. Severe dengue has a mortality rate of 5% if treated and 15% if left untreated.
Symptoms can include:
a high temperature, feeling hot or shivery
a severe headache
pain behind the eyes
muscle and joint pain
feeling or being sick
a widespread red rash
tummy pain and loss of appetite
These suggestions may help to relieve symptoms:
Take paracetamol to relieve pain and fever
Do NOT take aspirin or ibuprofen, as these can cause bleeding problems in people with dengue
Drink plenty of fluids to prevent dehydration – bottled water is safer than tap water in many locations
Get plenty of rest
You should start to feel better after about a week, although it may be a few weeks before you feel your normal self again. Get medical advice if your symptoms don't improve and be aware that you can get it again if you've had it before, as you'll only be immune to one type of the virus.
It’s thought that people who've had dengue before are at most risk of severe dengue (or dengue haemorrhagic fever) if they become infected again. So this makes it a bigger risk for mariners working particular routes, than for tourists or travellers. It may also go untreated if you are some distance from medical care (or can’t afford it), or if dengue isn’t diagnosed in time.
Signs of severe dengue can include:
Severe abdominal pain.
Swollen or distended abdomen.
Vomiting repeatedly, vomiting blood.
Bleeding gums or bleeding under the skin.
Breathing difficulties or fast breathing.
Cold, clammy skin.
A weak but fast pulse.
Drowsiness or loss of consciousness.
As we said earlier, prevention is the best attack and these actions can reduce your risk of being bitten:
Use insect repellent – products containing 50% DEET are most effective, but a lower strength (15 to 30% DEET) should be used on children, and alternatives to DEET should be used on children younger than 2 months.
Wear loose but protective clothing – those pesky mosquitoes can still bite through tight-fitting clothes. Trousers, long-sleeved shirts, and socks and shoes (not sandals) are best.
Sleep under a mosquito net – ideally one that has been treated with insecticide, or keep screens closed.
Be aware of your environment – mosquitoes that spread dengue breed in still water in urban areas so drain any standing water and discard any item where water could collect.
So what can you do? As we’ve mentioned before, the vast majority of diseases begin with ‘flu-like symptoms’. So, keep an eye on the current status of dengue and other infections in the area that you’re travelling to or from.
We recommend the National Travel Health Network and Centre website www.nathnac.net as a great resource. If you or a colleague suffers from flu-like symptoms, just bear in mind that it could be dengue, even in areas not known for it, and ask for it to be considered during any medical consultation.
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