Public Transport Users at Risk for Respiratory Infection

Summary
An epidemiological study was conducted to explore the association between recent public transport use and the likelihood of acquiring acute respiratory infection during the 2008-09 flu season. The findings of the study suggest that recent use of public transport does pose a risk for the acquisition of acute respiratory infection. The risk appeared to be greatest among occasional users rather than habitual public transport users.

Introduction
The current guidelines during flu epidemics and pandemics suggests having good respiratory hygiene and courtesy, and refraining from making unnecessary travel by taking public transport when symptomatic. However, there are no studies that directly support or refute an association between the use of public transport and acquiring an acute respiratory infection. A recently published observational study suggests no association between the seasonal flu virus and regular public transport use. Hence, the authors conducted an analysis of patients visiting a general practitioner during a winter seasonal flu outbreak to explore the likelihood of acquiring a respiratory infection by using public transport immediately preceding the onset of the illness.

Methodology

  • Patients visiting a general practitioner (GP) during the winter season were segregated into two groups: patients with acute respiratory infection (classified as cases) and patients visiting due to any non-respiratory acute condition (classified as controls).
  • Data were obtained on bus or tram usage in the five days preceding illness onset (cases) or before consultation (controls) along with demographic details of the patients using a questionnaire.
  • Data were also obtained regarding the frequency of public transport usage.
  • Key findings

  • It was found that the “cases” group were six times more likely to have travelled by public transport in the five days before symptom onset than the “control” group. This, however, was not significant statistically.
  • The risk of acquiring infection is less among regular users of public transportation.
  • Occasional users of public transportation have the greatest risk of acquiring respiratory infection.
  • Shortcomings
    The cases were not confirmed by serological examination of influenza virus and therefore the range of respiratory virus aetiologies was not known. Also, it could not be confirmed from the control group whether the participants had already acquired respiratory infection symptoms earlier in the flu season that could have led to acquired immunity in the controls. The study also lacked on gathering data about the subject’s normal working environment (e.g., whether working in close contact with many people) and the usage of public transport during rush hour or off-peak travel times. Lastly, the study had weak associations that were not statistically significant due to the limited sample size.

    Conclusion
    The study found an association between recent public transport use and likelihood of acquiring a respiratory infection. The risk was more among occasional users of public transport, rather than the habitual users. The authors suggest that frequent traveling makes an individual more exposed to the viruses and, hence, leads to the development of immunity against the exposed virus. ”The findings support current public advice to exercise good respiratory hygiene and existing pandemic guidance to refrain from making unnecessary journeys by public transport when symptomatic.” The findings therefore support that mass transport systems should not be routinely suspended during a pandemic outbreak of influenza. Further studies are required to investigate and evaluate the frequency of habitual use of public transport in relation to acquisition of infection during a relevant incubation period for the microbial agent.

    For More Information:
    Public Transport Use May Pose a Risk for Acquisition of Acute Respiratory Infection
    Publication Journal: BioMed Central Infectious Diseases, 2011
    By Joy Troko; Puja Myles; Division of Epidemiology & Public Health, University of Nottingham, Clinical Sciences Building, City Hospital, Nottingham, UK

    *FYI Living Lab Reports Are Summaries of the Original Research.
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