Dipti Patel1, Hilary Simons2, Patricia Schlagenhauf3. 1. National Travel Health Network and Centre (NaTHNaC), UCLH NHS Foundation Trust, London, NW1 2PG, UK. Electronic address: dipti.patel9@nhs.net. 2. National Travel Health Network and Centre (NaTHNaC), UCLH NHS Foundation Trust, London, NW1 2PG, UK; National Travel Health Network and Centre (NaTHNaC), Liverpool School of Tropical Medicine, Pembroke Place Liverpool, L3 5QA, UK. 3. University of Zurich Centre for Travel Medicine, WHO Collaborating for Travellers' Health, Department of Public Health, Institute for Epidemiology, Biostatistics and Prevention, Hirschengraben 84, 8001, Zurich, Switzerland.