key: cord-0888281-gx5rni2t
authors: Dao, Thi Loi; Canard, Naomie; Hoang, Van Thuan; Anh, Ly Tran Duc; Drali, Tassadit; Ninove, Laetitia; Fenollar, Florence; Raoult, Didier; Parola, Philippe; Marty, Pierre; Gautret, Philippe
title: Risk factors for symptoms of infection and microbial carriage among French medical students abroad
date: 2020-09-02
journal: Int J Infect Dis
DOI: 10.1016/j.ijid.2020.08.075
sha: 353f7b96abe55fd89248f649c76ff99d90a19e52
doc_id: 888281
cord_uid: gx5rni2t

Objectives To investigate symptoms of infections and their risk factors among French medical students undertaking an internship abroad. Methods Clinical follow up and qPCR-based respiratory, gastrointestinal, and vaginal pathogen carriage were prospectively assessed pre-travel and post-travel, in a cohort of medical students departing from Marseille, France. Results 293 students were included. 63.5%, 35.8% and 3.6% of students reported gastrointestinal, respiratory, and vaginal symptoms, respectively. The acquisition rate of Enteroaggregative Escherichia coli and Enteropathogenic E. coli was 40.9% and 18.6%, respectively. A significant increase was observed for rhinovirus and Streptococcus pneumoniae by comparing the prevalence of pathogens in pre-travel and post-travel samples. Gardnerella vaginalis and Atopobium vaginae acquisition rates were 12.9% and 13.9%, respectively. Being female, primarily travelling to Vietnam, and living in basic accommodation conditions were independent risk factors for reporting respiratory symptoms. Students reporting respiratory symptoms were three times more likely to acquire S. pneumoniae. Travelling primarily to north India and Senegal were independent risk factors for diarrhoea. Conclusion This study makes it possible to identify the main infectious diseases linked to travel in a group of French medical students undertaking an internship abroad and the risk factors on which to base targeting students for reinforced pre-travel advice.

International travellers are exposed to the acquisition of potential pathogens including viruses, bacteria or parasites with the risk of community or hospital spread upon return, whether or not they present health problems during their trip. Therefore, there is a risk of pathogens being imported into France from endemic areas abroad, either from foreign travellers visiting France, from French travellers visiting foreign countries, or via migrants and expatriates treated in France with a risk of indigenous spread. This has been extensively described, by example, among French Hajj pilgrims travelling to Mecca, Saudi Arabia [1].

An Australian organisation, Work the World, has enabled 15,000 medical students to take part in internships abroad since 2005 [2] . Developing countries are becoming popular destinations of internship. Medical internships abroad are generally hospital immersion experiences but, young medical students also participate in humanitarian missions that are unrelated to clinical activities such as school renovation for example [3, 4] . In one Australian survey, 64% of students experienced some sort of health problems while taking part in electives abroad, and travellers' diarrhoea was the most common problem (40%) [5] . In our preliminary report on a cohort of 134 French medical students participating in international electives, we showed that 73.9%, 38.8% and 5% of them reported gastrointestinal, respiratory, and vaginal symptoms, respectively [4] . We showed that the acquisition rate of Enteropathogenic Escherichia coli (EPEC) and Enteroaggregative E. coli (EAEC) was 41% and 53%, respectively. By contrast, the acquisition of respiratory viruses was low but was associated with persistent respiratory symptoms at return. Respiratory bacterial acquisition ranged from 3.3% for Streptococcus pyogenes to 15.0% for Haemophilus influenzae. Atopobium vaginae and Gardnerella vaginalis percentage of acquisition were 14.3% and 7.7%, respectively. So far, to our knowledge, the risk factors for acquisition of pathogens have not been clearly identified among medical students abroad to date. The relationship between symptoms and the carriage of pathogens J o u r n a l P r e -p r o o f also remain poorly understood, making it difficult to distinguish between infection and colonisation.

We aim to conduct this study to investigate the risk factors for symptoms of infections among French medical students undertaking an internship abroad.

A monocentric prospective cohort survey was conducted over two years (2018-2019) among medical students from the Faculty of Medicine in Marseille, France who were planning to take part in an internship abroad during the summer. Recruitment was performed on a voluntary basis, during their vaccination and pre-travel consultation at the Institut Méditerranée Infection which is on the Marseille University medical campus. Participants were asked to complete an inclusion questionnaire including demographic data, history of chronic illness, intended travel dates and destination. All participants received advice regarding the prevention of diarrhoea during travel (hand hygiene, safe food, and water habits) but prophylaxis for traveller's diarrhoea was not prescribed. Because dates of departure and return are different for each student, the samples were not taken at once. The participants were given two sets of "pre-travel" and "post-travel" kits which contained questionnaire and sampling equipment (commercial rigid cotton-tipped swab applicators and viral transport media). They were also instructed how to self-collect samples, as following: 3 cm in the nostril, 5 turns and post wall of the pharynx, 5 streaks for respiratory samples; rectal samples were collected using two methods: rectal self-sampling when having a bowel movement, 3 centimetres through the anus, gently rubbing the inner walls of the rectum several times or stool collection after emission; vaginal samples were collected by placing the swab about three centimetres in the vagina and gently rubbing the inner walls several times, avoid touching the skin and vulva with the swab. Samples were self-collected using commercial rigid cotton-tipped swab applicators (Medical Wire & Equipment, Wiltshire, UK) and placed in viral transport media (Sigma Virocul®) for further process at our laboratory. A document of instructions for self-sampling was also provided in the kits. During the week before travel, each student was invited to deposit their self-collect samples and a pre-travel questionnaire that collected information about their health problems and antibiotic use if applicable. After their travel, they were invited to self-collect samples during the week following their return to France. Students were also provided with a post-travel questionnaire addressing the exact place of the internship, the type of activities during their stay, including tourism and travel to other countries over the internship period. Accommodation conditions, contact with animals or children, symptoms, onset of symptoms and treatment during their stay were also documented. Influenza-like illness (ILI) was defined as sore throat, cough plus subjective fever [6] . Diarrhoea was defined by at least three loose or liquid stools per 24 hours.

The methods for identifying respiratory, gastro-intestinal, and vaginal pathogens by PCR assay are detailed elsewhere [4] . The followed respiratory pathogens were screened: Influenza A 

PCR were considered positive for virus or bacteria detection when the cycle threshold (CT) value was ≤35. Bacterial vaginosis was defined by a G. vaginalis DNA load ≥ 10 9 copies/mL (CT≤ 18) and/or an A. vaginae DNA load ≥ 10 8 copies/mL (CT≤ 21), as previously reported [7] .

The acquisition of a pathogen was defined as negative before travel and positive when returning to Marseille, France.

STATA software version 14.2 was used to conduct statistical analysis. Differences in the proportions were tested by using Fisher's exact or Pearson's chi-square tests, when appropriate.

McNemar's test was used to evaluate the potential acquisition of pathogens (prevalence after versus before travel). Clinical symptoms during travel were reported only if onset of symptoms took place during travel. Univariate analysis was used to evaluate unadjusted associations between the prevalence of symptoms during travel and multiple factors. A p-value <0.05 was considered to be statistically significant. Only variables with a prevalence equal or more than 5.0% were considered for statistical analysis. Variables with p-values <0.2 in the univariate analysis were included in the multivariate analysis. Log-binomial regression was used to estimate factors' adjusted risk ratios for symptoms of infections.

The protocol was approved by our Institutional Review Board (2019-006). It was performed in accordance with the good clinical practices recommended by the Declaration of Helsinki and its amendments. All participants gave their written informed consent.

A total of 293 students agreed to participate and answered the post-travel questionnaire. The M/F gender ratio was 0.31 with a median age of 21 years (ranging from 18 to 25 years). Most participants (80.9%) were students in their second year of medical studies and were taking part in a non-medical humanitarian mission. The remaining participants were in their 4 th year of study and were assigned to different departments of medicine or surgery for clinical training (Supplementary Table S1 ). Overall, 5.1% took antibiotics in the week before departure and 17.8% took doxycycline as a chemoprophylaxis against malaria during their stay.

J o u r n a l P r e -p r o o f between arrival at the travel destination and the onset of symptoms was 17 days [ranging from 1 to 58 days]. The most frequent respiratory symptoms were rhinitis (27.1%), sore throat (21.8%) and cough (20.1%), followed by fever (9.6%) and dyspnoea (6.5%) (Figure 1a) . 7.9% of students declared persistence of symptoms on their return to France and 5.5% took antibiotics (ATB) for respiratory symptoms during travel.

A total of 275 (93.9%) students provided paired nasopharyngeal swabs. 52.4% of students acquired at least one respiratory pathogen. 17.8% of (49/275) students acquired at least one respiratory virus with human rhinovirus (14.6%) being the most frequent. Twenty-three students were still symptomatic after returning to France. Of whom, 16 (69.6%) were positive for at least one pathogens. Bacterial acquisition rates were higher (40.7%), with S. aureus (18.9%) being the most frequent, followed by H. influenza (17.1%) ( Table 1) . A total of 6.2% students acquired a virusbacteria combination and 11.6% a bacteria combination. When comparing the post-versus pretravel prevalence of pathogens, a significant increase was observed for rhinovirus and S. pneumoniae.

A proportion of 63.5% of students reported at least one gastro-intestinal symptom, all during travel and only one following return. The median time between arrival at the travel destination and the onset of symptoms was 13 days [ranging from 1 to 65 days]. The most frequent symptoms were diarrhoea (48.1%) and abdominal pain (46.4%), followed by nausea (26.3%) and constipation (19.8%) (Figure 1b ). 8.9% reported persistent symptoms on return to France and 3.4% took an antibiotic for diarrhoea during their stay.

J o u r n a l P r e -p r o o f gastrointestinal symptoms at day 1 after departure. But all rectal samples pre-travel were negative for gastrointestinal pathogens. 51.5% students acquired at least one gastrointestinal pathogen. Nine students (3.3%) acquired at least one virus (adenovirus, astrovirus and norovirus). Bacterial acquisition rates were higher (49.3%), notably for EAEC (40.9%) and EPEC (18.6%). Additionally, 2.6% of individuals acquired Shigella spp/EIEC, 1.5% Salmonella spp and 1.1% G. lamblia (Table   2 ). When comparing the post-versus pre-travel prevalence of pathogens, a significant increase was observed for viruses overall, EAEC, EPEC, Salmonella spp and Shigella spp/EIEC.

Of the 224 female students, eight (3.6%) reported vaginal symptoms such as leucorrhoea, during their stay, and two took antibiotics for this purpose. vaginalis (12.9%) ( Table 3) . Nine students (4.0%) had molecular criteria for bacterial vaginosis on return. When comparing the post-versus pre-travel prevalence of microorganisms, a significant increase was observed for G. vaginalis (CT<18), indicative of vaginosis.

Being female, primarily travelling to Vietnam, and living in basic accommodation conditions were independent risk factors for reporting respiratory symptoms. Students suffering respiratory symptoms were 3 times more likely to acquire S. pneumoniae during travel. Travelling primarily to north India and Senegal were independent risk factors for reporting diarrhoea (Table 4) . Overall, symptoms were relatively mild with fewer than 5% students requiring antibiotics and most symptoms resolved before students came back to France. This result is consistent with other studies realized on medical students abroad, confirming the fact that despite reinforced pre-travel counselling, travel-associated respiratory infections and travellers' diarrhoea were very frequent among medical students who were fully aware of the ways to prevent these illnesses [5, [8] [9] [10] .

We found a significant acquisition of human rhinovirus and S. pneumoniae as reported previously among international travel as well as among Hajj pilgrims [1, 11, 12] . We also observed a high acquisition rate of EAEC (40.9%) and EPEC (18.6%) among health students, as documented in other studies realized in different populations of domestic and international travellers [13] [14] [15] [16] [17] [18] .

Our results showed that respiratory symptoms were significantly more frequent in female. We have no explanation for this observation. Interestingly, the travel destination was distinctly associated with symptoms. Travel to India and Senegal was a risk factor for diarrhoea while travel to Vietnam was a risk factor for respiratory symptoms. Our results are discordant with those of a previous study J o u r n a l P r e -p r o o f on 649 international travellers showing that respiratory infections (sore throat or cough) were significantly increased in travellers returning from the non-tropical regions (7.6%) than those from tropical regions, including Vietnam (2.0%) [19] . Differences by travel destination are also known to be relative to the incidence of travellers' diarrhoea. This result was in line with most other studies that have also found that travelling to the Indian subcontinent was a highest relative risk for diarrhoea, followed by African regions [16, [20] [21] [22] [23] .

In addition, the observed correlation between respiratory symptoms and very basic accommodation conditions suggests that precarious housing conditions may encourage respiratory infections. A significant association between the acquisition of S. pneumoniae and respiratory symptoms was also observed in cohorts of Hajj pilgrims [24] .

We observed no significant association between E. coli acquisition and diarrhoea in our study, in contrast to other studies where EAEC or EPEC have been reported to be more frequent in travellers with diarrhoea returning from several geographical areas [14, 16, 25] . This may be explained by the onset of gastro-intestinal symptoms occurring early during the trip, while sampling was performed on return, several weeks later. Furthermore, asymptomatic carriage of potential pathogens was also observed in participants. In a study by Adachi et al., EAEC was detected in the stools of 26% of patients with traveller's diarrhoea returning from Mexico, Jamaica, or India [26] . On the other hand, a recent case-controlled study conducted on German and Dutch travellers showed that EAEC detection was not significantly different in diarrheal persons and asymptomatic controls. However, the prevalence of this bacterium among participants suffering from diarrhoea during international travel was high (40.0%) [14] . Such results are in line with ours.

Our study has a few limitations. First, this study was monocentric and conducted on a very specific population of travellers which impairs generalisation of our findings. Also, qPCR does not J o u r n a l P r e -p r o o f differentiate between dead and viable microorganisms. Finally, sampling was realized during the week preceding departure and during the week following return, samples at onset of symptoms were not available. Among students who reported clinical symptoms early after their arrival abroad, we are not sure whether these students were infected before or after departure, since incubation times of diseases are very different and may vary (Supplementary table S3 

The authors declare that there are no conflicts of interest. 

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