Measles associated with international travel in the region of the Americas, Australia and Europe, 2001–2013: A systematic review

Summary

Background

Travel volumes are still increasing resulting in a more interconnected world and fostering the spread of infectious diseases. We aimed to evaluate the relevance of travel-related measles, a highly transmissible and vaccine-preventable disease.

Method

Between 2001 and 2013, surveillance and travel-related measles data were systematically reviewed according to the PRISMA guidelines with extraction of relevant articles from Medline, Embase, GoogleScholar and from public health authorities in the Region of the Americas, Europe and Australia.

Results

From a total of 960 records 44 articles were included and they comprised 2128 imported measles cases between 2001 and 2011. The proportion of imported cases in Europe was low at 1–2%, which reflects the situation in a measles-endemic region. In contrast, imported and import-related measles accounted for up to 100% of all cases in regions with interrupted endemic measles transmission. Eleven air-travel related reports described 132 measles index cases leading to 47 secondary cases. Secondary transmission was significantly more likely to occur if the index case was younger or when there were multiple infectious cases on board. Further spread to health care settings was found. Measles cases associated with cruise ship travel or mass gatherings were sporadically observed.

Conclusions

Within both, endemic and non-endemic home countries, pretravel health advice should assess MMR immunity routinely to avoid measles spread by nonimmune travelers. To identify measles spread as well as to increase and sustain high vaccination coverages joint efforts of public health specialists, health care practitioners and travel medicine providers are needed.

Introduction

Measles is an acute viral infection of the respiratory system easily transmitted among humans, mainly through droplets by coughing or sneezing [1]. Symptoms include fever, cough, coryza, conjunctivitis and are followed by a generalized, specific maculopapillar erythematous skin rash with an incubation period of seven to 21 days following exposure. Hospitalization rates are high and especially among adults complications are relatively common. The virus is shed for several days before the typical rash appears, which increases the risk of silent transmission. Immunization is the best preventive measure [1] but the vaccination coverage varies between the different regions of the world.

Since 2002, the Region of the Americas (North, Central, South America and the Caribbean) has achieved and maintained measles elimination reaching sufficient vaccination coverages. Australia also has interrupted endemic measles transmission and recently, has achieved measles elimination [2], [3]. However, in both regions, outbreaks still occur involving imported cases. In contrast, Europe, Africa and parts of Asia still suffer from endemic measles with outbreaks, e.g. between 2006 and 2009, 2011, and recently, in 2013. Therefore, spread of measles remains a relevant risk for non-immune international travelers and their contacts due to its easy spread and the varying regional vaccination coverage rates [4], [5], [6]. By the end of 2020, the World Health Organization targets to eliminate measles in at least five WHO regions [1].

Imported measles cases to regions with interrupted measles transmission can have substantial consequences. Therefore, our aim was to assess the relevance of both, travel-associated and imported measles cases to identify shared challenges as well as to evaluate data by mode of transportation and travel characteristics, including mass events.