Learning update: Travel health

A warmer climate, heatwaves and floods are making countries in Europe increasingly hospitable to mosquitoes, with the risk of diseases like dengue fever, yellow fever, chikungunya, Zika and West Nile virus growing to record levels (writes Christine Clark). 

In the past these were predominantly diseases of tropical and sub-tropical regions but, as a result of international travel and environmental factors, a few hundred cases are seen each year in the UK. Most have been acquired in Asia, the Americas and the Caribbean, where they are endemic.

Mosquito-transmitted viral infections

Mosquito-transmitted viral infections include yellow fever, dengue fever, chikungunya, Zika and West Nile virus. These are mainly transmitted by the Asian Tiger mosquito (Aedes albopictus), which has now been reported in much of Europe (See map for October 2023 status).

The tiger mosquito is smaller than the common mosquito, is silent in flight and feeds during the daytime. Travellers planning visits to areas where the infections are endemic need to plan ahead for vaccinations (if applicable) and insect protection equipment.  

Animal ticks can also be important vectors for infections (e.g. tick-borne encephalitis), and recently, sporadic cases of Crimean-Congo haemorrhagic fever (CCHF). 

Travellers who are backpacking or camping in rural areas are likely to be at higher risk. Up-to-date information about the diseases and affected areas is available on a number of websites including Travel Health Pro and NHS Fit for Travel.

Table 1 (below) summarises the important features about the most common insect- and tick-transmitted viral infections. Treatment for these viral infections relies on supportive care based on rest, hydration and analgesics. As there is no specific treatment, avoidance of infection is paramount. 

Avoiding bites 

Insect bites are common and usually cause only minor irritation but can trigger an allergic reaction, be very inflamed or get infected. In areas where there is vector-borne disease, precautions should be taken using a combination of the following avoidance measures:  

• Avoid areas of standing water where mosquitoes can breed
• Wear loose fitting, light-coloured clothes, long sleeves, long trousers
• Wear insecticide-impregnated (pre-treated) clothing
• Apply DEET-based repellents to clothing and exposed skin. If DEET is not tolerated, use an alternative (e.g. icaridin). Remember, DEET can damage plastics and artificial fibres, so care is needed to avoid contact with plastics (e.g. watch straps and sunglasses)
• Use air conditioning where available or sleep in screened accommodation, under a mosquito net impregnated with insecticide
• Use insecticide vaporisers at night
• Avoid walking through long grass to avoid tick bites; check body for ticks after outdoor activity and remove ticks promptly.

The following measures lack evidence and are not recommended: garlic, vitamin B1 (thiamine), vitamin B12, yeast extracts (e.g. Marmite), tea tree oil and homeopathic remedies. Further information can be found in the Insect and Tick Avoidance factsheet from Travel Health Pro.

Treating bites and stings

Inevitably, some bites and stings will occur. Wash with soap and water, and relieve pain and itching with a cold compress. Paracetamol or ibuprofen can be taken for pain; oral antihistamines for swelling and itching. A mild steroid cream is also good for itching. Keep the area clean and dry and avoid scratching.

After a honeybee sting, the sting should be removed as quickly as possible by scraping sideways with a nail or credit card. 

Ticks need to be removed from the skin very carefully to avoid leaving tick mouthparts in the skin. Fine-tipped tweezers or specially-designed tick removers should be used.

Rapid-onset reactions are likely to be allergic or inflammatory. Infected bites or stings will not be evident until 48 hours or more after the initial event. 

Malaria

Malaria is caused by protozoan parasite infection transmitted by the bite of Anopheles mosquitoes. An ABCD strategy is recommended: 

• Awareness: Know what type of malaria is prevalent and the level of risk. Check for the latest malaria information on Travel Health Pro
• Bite avoidance: Follow the measures outlined previously
• Chemoprophylaxis: Check latest information from UKHSA ACMP and its malaria prevention guidelines for travellers from the UK. The guidelines contain up-to-date detailed maps of all regions where malaria is reported, and details of chemoprophylaxis and emergency standby medication
• Diagnosis: Any febrile illness must be investigated promptly. 

Traveller’s diarrhoea

Diarrhoea is the most common illness affecting travellers. It can occur during travel or within 10 days of return, and can be very disruptive to travel plans. It may be viral, bacterial or protozoal in origin and is acquired from contaminated food or water.

Traveller’s diarrhoea is defined as three or more unformed stools in a 24-hour period, often accompanied by at least one of the following: fever, nausea, vomiting, cramps or bloody stools (dysentery). 

The risks of traveller’s diarrhoea are higher if sanitation is poor, food hygiene standards are low and there is limited access to clean water. 

An episode of diarrhoea and vomiting is usually self-limiting. However, oral hydration is important to prevent dehydration, especially in a hot climate. Proprietary rehydration solutions made up with clean drinking water are ideal but if not available, a salt and sugar solution of six level teaspoons of sugar and half a teaspoon of salt to one litre of ‘safe’ (e.g. freshly boiled and cooled) water can be used. 

Loperamide can be taken for short-term symptomatic relief, if required, by adults and children over 12 years. There is no place for prophylactic antibiotics and fluoroquinolones are no longer recommended for ‘standby’ treatment as resistance is an increasing problem. If visiting a high-risk area or remote location, expert advice for standby antibiotics should be sought. 

Sun safety and skin cancer

Enjoying the sun is one of the joys of travel, so it is important to avoid the short-term and long-term risks of over-exposure to UV radiation. These are – in the short term – sunburn; in the long-term skin cancers and cataracts. 

With more than 172,000 new cases of all types of skin cancer each year,1 it is the most common cancer in the UK and rates continue to rise. 

Non-melanoma skin cancers (NMSC) – basal cell carcinomas and squamous cell carcinomas – account for about 90 per cent of skin cancers and are more common in the over-70s. Melanomas are much rarer but more dangerous as they can metastasise and be fatal. NMSCs and early-stage melanomas are treated via surgical excision.

Sunburn is a clear sign that the DNA in skin cells has been damaged by too much UV radiation. Getting sunburnt just once every two years can triple the risk of melanoma skin cancer, compared to never being burnt.¹ However, there can be a long time lag – skin cancers may not develop until 10 or 20 years after the excessive exposure. A booklet (with pictures) to help identify skin cancers can be downloaded from the Skcin website. 

The main preventable cause of skin cancer is excessive exposure to UV light from sunlight or other sources (e.g. UV tanning beds). 

Some people are at greater risk than others (e.g. those with pale skin, often associated with blue eyes and blonde or red hair and those with a personal or family history of skin cancer). Other risk factors include frequent or intense exposure to UV radiation (e.g. outdoor work and sunbed use), immunosuppression (e.g. organ transplant recipients), large numbers of freckles or moles, extremes of age and exposure to chemicals (e.g. petroleum products).  

Organ transplant recipients

Organ transplant recipients are immuno-suppressed and at high risk of developing actinic keratoses (AKs) that can be precursors of skin cancer. They need to use year-round, high-factor sunscreens on all exposed skin and should take nicotinamide 500mg twice daily to prevent AK and NMSC.² 

Vitamin D levels

Adequate vitamin D levels are thought to have a protective effect, decreasing melanoma cancer risk and mortality.³ Sunscreens and sun-avoidance can result in vitamin D deficiency. Vitamin D doses of 800-4000IU/day (depending on circumstances and needs) are recommended.⁴