1 National Travel Health Network and Centre, and London School of Hygiene and Tropical Medicine, Hospital for Tropical Diseases, London WC1E 6JB
2 Travelers’ Advice and Immunization Center, and Tropical and Geographic Medicine Center, Massachusetts General Hospital, Boston, USA
Correspondence to: D R Hill [email protected]
Contributors: DRH planned the paper, wrote the first draft, and is the guarantor. ETR contributed to the content, helped to revise the paper, and agreed to the final submission.
Competing interests: None declared.
Provenance and peer review: commissioned; externally peer reviewed.
doi:10.1136/bmj.a1746
