Travel abroad is linked to a large proportion of infections in the English region

International travel is a major risk factor for developing a range of infections, according to a study in a region of England.

Scientists have found that illness after traveling abroad contributes substantially to the burden of infection in North East England. Since 2013, there has also been no decrease in the share of travel-related infections in non-pandemic years.

Laboratory reports of common notifiable enteric infections were linked to exposure data for cases reported between January 2013 and December 2022. The results were published in the journal Epidemiology and infection.

Pathogens behind diseases
A total of 9,358 laboratory-confirmed cases of gastrointestinal illness due to infection with Cryptosporidium, Giardia, hepatitis A, Salmonella, Shigella, Shiga toxin-producing E. coli (STEC), Vibrio and Yersinia were reported in residents of North East England . Routine exposure questionnaires were completed for 7,909 cases.

About 35 percent of cases reported international travel during the incubation period, although the number of travel-related cases dropped significantly during the COVID-19 pandemic.

Between 2013 and 2019, half of Shigella and non-typhoidal Salmonella infections and a third of Giardia infections were reported after travel. This figure was below 30 percent for Cryptosporidium and above 20 percent for STEC infections.

In England, all laboratory-confirmed cases of notifiable enteric infections from National Health Service (NHS) laboratories are reported to the UK Health Security Agency (UKHSA) via the Second-Generation Surveillance System (SGSS). North East England has its own surveillance system, which links routinely collected SGSS data, laboratory typing data and exposure data from standardized exposure questionnaires.

Cases were defined as associated with international travel if they had a completed exposure questionnaire and reported having been outside Britain for a specified incubation period. The proportion of cases linked to international travel remained consistent between 2013 and 2019 at an average of 38 percent.

During the UK response to the COVID-19 pandemic in 2020 and 2021, infections were much lower than historical rates. In 2022, reports returned to pre-pandemic levels, mainly due to the increase in travel-related cases.

Risky destinations
The proportion of cases associated with travel remained consistent for most pathogens, with the exception of Shigella, which has seen an increase in UK-acquired cases since 2013, and STEC O157, which saw an increase in internationally acquired cases in 2019 cases were reported.

Children under the age of 9 and adults over 60 were significantly more likely to contract the infection in Britain.

Where such data was available, people of Asian ethnicity were more likely to acquire their infection during international travel, with the rate of reported travel-related infections among people of Asian ethnicity significantly higher than the rate among people of white ethnicity.

The most common destination reported by the cases was Spain, followed by Turkey, India and Egypt. Disease rates were highest among people returning from Africa and Asia, and high rates were also associated with all-inclusive tourist resorts such as Turkey, Egypt and the Dominican Republic.

Rates of hepatitis A and typhoid Salmonella were highest among travelers to Asia, and rates of Vibrio were similar for travelers to both Africa and Asia. Rates for all other pathogens were highest in people returning from Africa. The rate of non-typhoidal Salmonella infections was 527 times higher in travelers to Asia compared to travelers to Europe.

More than 50 Salmonella and 41 Cryptosporidium clusters were identified. Salmonella outbreaks were mainly linked to travel to Turkey, Egypt and Mexico. Outbreaks of Cryptosporidium were mainly associated with Spain, Turkey, the Canary Islands and Egypt.

“This work highlights the need to better understand risks during travel, to support the implementation of guidance and control measures to reduce the burden of disease in returning travelers,” researchers said.

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