COVID-19 aside, international travel is easier and more prevalent than ever before, and illness associated with travel is common. Although most infections contracted overseas are self-limiting and mild, they often present with non-specific symptoms such as fever, making them very challenging to initially differentiate from more severe diseases.

Key Points

• International travel is common, and illness associated with travel occurs frequently.
• Using a full or focused travel history can help identify causes of fever in the returning traveller.
• Malaria is a common cause of fever in the recently returned traveller, however, non-tropical infectious diseases should also be considered.
• Isolating potentially infectious patients and informing public health agencies of notifiable diseases are important actions.

Causes of Fever

There are a number of potential causes of fever in the returning traveller, including several infectious tropical and subtropical diseases. While some infectious diseases are distributed globally, others are found only in specific countries or regions. Furthermore, the weather and season can also influence the prevalence of certain diseases.

Despite technological and healthcare advances leading to reductions in infectious diseases, better access to prophylactic medication, and information about effective preventative measures, travellers are still at risk of contracting illnesses endemic to specific regions.

As such, taking a detailed travel history helps to identify which infectious diseases to consider when presented with fever in a recently returned traveller. It is also important to consider whether a non-tropical disease could be the cause e.g. upper and lower respiratory tract infections or a urinary tract infection.

Malaria

Malaria is an important cause of fever in the recently returned traveller. Around 1500 cases of malaria are reported each year in the UK, with eight or fewer associated deaths per year.

It is caused by plasmodium parasites and spread by mosquito bites. There are five types of malaria parasites that can infect humans – P. falciparum, P. vivax, P. ovale, P. malariae, and P. knowlesi – which typically infects macaques in Southeast Asia but can also affect humans. Overall, P. falciparum is the most common species.

At present, malaria is usually restricted to tropical and subtropical areas at altitudes lower than 1500m, though there are concerns that climate change may change the distribution of vector-borne diseases in coming years. Factors such as the geographical region, season, type of accommodation, and adherence to prevention measures all contribute to the overall risk of contracting malaria.

The P. falciparum malaria lifecycle involves human and female Anopheles mosquito stages.

Symptoms of malaria

• The symptoms of malaria can vary from mild to life-threatening.
• All of the clinical symptoms are caused by the asexual erythrocytic (blood) stage of the life cycle.
• Common presenting symptoms of patients with malaria are a combination of fever, rigors, sweats, headaches, nausea, vomiting, general malaise, and generalised pain.
• These symptoms in patients in countries with a low incidence of malaria could be mistaken for common infections such as influenza, coryzal illness, and urinary tract infections. Therefore, asking if a patient has recently travelled is a key diagnostic tool.

Other important potential causes of fever in the returning traveller include enteric fever, hepatitis A, and influenza.

Travel History

Adapted from Leggat (2007)

• Which countries and regions did you visit
• Dates of travel (departure & return date)
• Did you travel in urban or rural areas
• What was the reason for your travel?
  • Tourism
  • Visiting friends or relatives
  • Business
  • Other
• Did you participate in any special activities?
  • Mountaineering
  • Scuba diving
  • Caving
  • Other
• Did you experience any specific risk exposures?
  • Sexual risks
  • Poor quality water or food
  • Ticks or other insect bites
  • Swim in lakes
  • Contact with wildlife
• Which vaccinations did you receive before travelling?
• Did you take malaria prophylaxis? And if so:
  • Which drug(s)?
  • When did you start it?
  • Did you take it as directed/were there any missed doses?
  • Are you still taking it?
• Did you become ill while away?
• Did anyone with you become ill?

It would be challenging to cover all of these questions in a short GP consultation appointment, but if there is concern of a tropical cause of fever this would aid diagnosis and inform necessary investigations.

Assessment & Investigations

• Note whether the patient has any pre-existing co-morbidities, such as diabetes, lung disease, or immunosuppression secondary to cancer or HIV, which may affect their presentation and management.
• All returning travellers with fever should be initially assessed for any signs of serious and life-threatening infection, such as sepsis, which may require urgent referral or treatment.
• Many cases of fever in the returning traveller will not have any specific features. However, physical examination should look for any signs of hepatomegaly, splenomegaly, lymphadenopathy, rash, eschars (dark crusted bites), urticaria, jaundice, haemorrhage, or meningism.

Initial investigations required may include:

• FBC, LFTs, U&Es
• Blood cultures
• Malaria films or rapid diagnostic test
  • The gold-standard method for diagnosing malaria is identification of malarial parasites on thick and thin blood films. The thick film should be used for the detection of malaria parasites and the thin film for identification of species)
• HIV test
• Urine and stool culture
• Chest X-Ray / USS of liver and spleen
• Serology / PCR for specific diseases (e.g. dengue or other arboviruses)

Isolate & Notify

• Infection prevention and control precautions are often needed until a diagnosis is confirmed and treatment can be started.
• Always follow local protocols, however, it is advisable to implement precautions for a patient that presents with fever and any one of the following: rash, diarrhoea, respiratory symptoms, haemorrhage, gastrointestinal or respiratory secretions.

• If you clinically suspect that a patient may have a notifiable disease, then this should be reported to local public health agencies.
• Public Health England works to identify possible outbreaks of diseases as rapidly as possible, and notification of possible cases is key to achieving this.
• Notifiable Diseases: Registered medical practitioners have a statutory duty to notify the ‘proper officer’ at their local council or local health protection team of suspected cases of certain infectious diseases. A full list of notifiable illness may be found via government guidance.  

References & Resources

• Bell DJ. Fever in the returning traveller. J R Coll Physicians Edinb. 2012; 42:43–6. Available from: https://www.rcpe.ac.uk/sites/default/files/bell.pdf
• Centres for Disease Control and Prevention: Malaria. Available from: https://www.cdc.gov/malaria/about/disease.html
• Doug F, Wani RS, Johnston V. Fever in the returning traveller. BMJ. 2018;360:j5773. Available from: https://doi-org.ezproxy3.lib.le.ac.uk/10.1136/bmj.j5773
• Gov.uk: Notifiable diseases and causative organisms: how to report. Available from: https://www.gov.uk/guidance/notifiable-diseases-and-causative-organisms-how-to-report
• Leggat PA. Assessment of febrile illness in the returned traveller. Australian Family Physician. 2007; 36(5). Available from: https://www.racgp.org.au/afp/200705/200705leggatt.pdf
• Lo Re V 3rd, Gluckman SJ. Fever in the returned traveler. Am Fam Physician. 2003 Oct 1;68(7):1343-50. PMID: 14567489.
• Mirski T, Bartoszcze M, Bielawska-Drózd A. Globalizacja a choroby zakaźne [Globalization and infectious diseases]. Przegl Epidemiol. 2011;65(4):649-55. Polish. PMID: 22390054
• NaTHNaC: Malaria. Available from: https://travelhealthpro.org.uk/disease/113/malaria

Written by Dr Megan S. Evans (Speciality Registrar in Public Health Medicine/Academic Clinical Lecturer) and Dr Hareen De Silva (GP)
Edited by Mudassar Khan (Y3 Medical Student)