Risk of infection following a visit to the emergency department: a cohort study

Background:

The risk of infection following a visit to the emergency department is unknown. We explored this risk among elderly residents of long-term care facilities.

Methods:

We compared the rates of new respiratory and gastrointestinal infections among elderly residents aged 65 years and older of 22 long-term care facilities. We used standardized surveillance definitions. For each resident who visited the emergency department during the study period, we randomly selected two residents who did not visit the emergency department and matched them by facility unit, age and sex. We calculated the rates and proportions of new infections, and we used conditional logistic regression to adjust for potential confounding variables.

Results:

In total, we included 1269 residents of long-term care facilities, including 424 who visited the emergency department during the study. The baseline characteristics of residents who did or did not visit the emergency department were similar, except for underlying health status (visited the emergency department: mean Charlson Comorbidity Index 6.1, standard deviation SD] 2.5; did not visit the emergency department: mean Charlson Comorbidity index 5.5, SD 2.7; p < 0.001) and the proportion who had visitors (visited the emergency department: 46.9%; did not visit the emergency department: 39.2%; p = 0.01). Overall, 21 (5.0%) residents who visited the emergency department and 17 (2.0%) who did not visit the emergency department acquired new infections. The incidence of new infections was 8.3/1000 patient-days among those who visited the emergency department and 3.4/1000 patient-days among those who did not visit the emergency department. The adjusted odds ratio for the risk of infection following a visit to the emergency department was 3.9 (95% confidence interval 1.4–10.8).

Interpretation:

A visit to the emergency department was associated with more than a threefold increased risk of acute infection among elderly people. Additional precautions should be considered for residents following a visit to the emergency department.Infections associated with health care are an important health risk. A recent survey by the World Health Organization reported that 8.7% of patients in hospital developed such infections.^1,2 The third leading cause of death in the United States is health care–associated deaths, with over 100 000 people dying from infections associated with health care each year.³ In Canada, a point-prevalence survey found that 11.6% of adults in hospital experience a health care–associated infection.⁴Little attention has been paid to infections acquired in other health care settings. Visiting an emergency department has been identified as a risk for disease during outbreaks of measles^5,6 and SARS,^7,8 but little is known about the potential risk of endemic infection from exposure in this setting. A visit to the emergency department differs from a stay in hospital: exposure and duration of contact with other patients is shorter, but the number and density of patients with acute illness with whom there could be contact is higher.Elderly residents of long-term care facilities are likely to be at the greatest risk of morbidity and mortality from communicable diseases acquired in the emergency department. When residents are transferred to the emergency department for assessment, they are likely to have longer stays and to be cared for in multibed observation areas and corridors.⁹ If they acquire an infection while in the emergency department, these residents may be the source of an outbreak upon return to their facility; this can lead to increases in workload and costs. A Canadian study estimated the cost of an influenza outbreak to be over $6000 per 30-day period, with an estimated incidence of death of 0.75/100 residents during the same period.¹⁰ In this study, we explored the risk of acute respiratory and gastrointestinal infection associated with a visit to the emergency department among elderly residents of long-term care facilities.