Epidemiology of imported infectious diseases, China, 2014-18

The frequent movement of population between countries brings an increasing number of travel-related infections. This study aims to define the spectrum and dynamics of imported infections observed from international travel in the Chinese mainland.

Sick travellers were screened by inbound sentinel surveillance and post-travel clinic visits from 2014 to 18. The infections were classified as respiratory, gastrointestinal, vector-borne, blood/sexually transmitted and mucocutaneous. The analysed variables included the place of origin of the travellers (Chinese or foreign) and the time when travel-related infection was present (at the time of return, during travel and post-travel visits to the clinic).

In total, 58 677 cases were identified amongst 1 409 265 253 travellers, with an incidence of 41.64/million, comprising during-travel incidence of 27.44/million and a post-travel incidence of 14.20/million. Respiratory infections constituted the highest proportion of illnesses during travel (81.19%, 31 393 of 38 667), which mainly came from Asian countries and tourists; with influenza virus and rhinovirus infections being mainly diagnosed. Vector-borne diseases constituted the highest proportion of post-travel illnesses (98.14%, 19 638 of 20 010), which were mainly diagnosed from African countries and labourers; with malaria and dengue fever being mainly diagnosed. The differential infection spectrum varied in terms of the traveller's demography, travel destination and travel purpose. As such, a higher proportion of foreign travellers had blood/sexually transmitted diseases (89.85%, 2832 of 3152), while Chinese citizens had a higher prevalence of vector-borne diseases (85.98%, 19 247 of 22 387) and gastrointestinal diseases (79.36%, 1115 of 1405). The highest incidence rate was observed amongst travellers arriving from Africa, while the lowest was observed amongst travellers arriving from Europe.

The findings might help in preparing recommendations for travellers and also aid in primary care or other clinics that prepare travellers before trips abroad. The findings will also help to identify locations and the associated types of infections that might require attention.