Study finds link between public transport and risk of catching ARI

You are six times more likely to end up at the doctors with an acute respiratory infection (ARI) if you have recently used a bus or tram — but those who use buses or trams daily might well be somewhat protected compared with more occasional users.

These are the findings of a study carried out by experts at The University of Nottingham into the relationship between public transport and the risk of catching an ARI. Their findings have been published in the online Journal BMC Infectious Diseases.

Jonathan Van Tam, Professor of Health Protection in the School of Community Health Science and Director of the Health Protection Research Group said: "This is a small exploratory study whose findings require confirmation by a larger study. However, the findings justify the need to practice good respiratory and hand hygiene when using public transport during periods when winter viruses are circulating and where possible to avoid situations where you might spread your germs to others when you have a respiratory illness."

The relationship between public transport use and acquisition of ARI is not well understood but potentially important during epidemics and pandemics.

The research, funded by the Health Protection Agency, showed that recent bus or tram use within five days of symptom onset was associated with an almost six-fold increased risk of going to the doctors for ARI.

The case-control study, by University of Nottingham medical student Joy Troko, was carried out during the 2008/2009 influenza season. The study ran during a local flu outbreak between December 2 2008 (week 49) and January 15 2009 (week two) which peaked in week 51.

One hundred and thirty eight patients (72 cases of ARI and 66 control patients) from a Nottingham GP practice were asked to fill in a questionnaire on bus or tram usages in the five days preceding the onset of their illness or the five days before consultation.

Professor Van Tam said: "We found a statistically significant association between ARI and bus or tram use in the five days before symptom onset. The risk appeared greatest among occasional bus or tram users. These data are very plausible when we think about the greater likelihood of developing protective antibodies to common respiratory viruses if repeatedly exposed. The findings have differing implications for the control of seasonal acute respiratory infections and for pandemic influenza. In the latter case we don't have an opportunity to build up any immunity beforehand because it's, by definition, a new virus."