Influenza-like illness in residential care homes: A study of the incidence, aetiological agents, natural history, and health resource utilization

¹ The Chinese University of Hong Kong, Hong Kong
² Shatin Hospital, Hong Kong

^* To whom correspondence should be addressed. E-mail: dschui{at}cuhk.edu.hk.

Accepted 9 January 2008

	Abstract

Background: Influenza-like illness (ILI) among elderly living in residential care homes (RCHE) is a common cause for hospitalization. We examined the incidence, underlying aetiology, natural history and associated healthcare resource utilization related to ILI in the RCHE population.

Methods: A prospective study of ILI in 4 RCHEs in Shatin, HK, from Apr 2006 to Mar 2007 was conducted. Each RCHE was monitored daily for ILI occurrence, and followed up until resolution of illness or death. Clinical features were recorded whereas sputum, nasopharyngeal aspirate, blood, and urine specimens were examined for underlying aetiology.

Results: 259 episodes of ILI occurred in 194 subjects, with mild peaks in winter and summer, over a sustained level throughout the year. Infection agent was identified in 61.4% of all episodes, comprising bacterial infection in 53.3% and viral in 46.7%. Multiple infections occurred in 16.2% of subjects. The most frequent organisms were Streptococcus pneumoniae, followed by respiratory syncytial virus, Pseudomonas aeruginosa, Metapneumovirus and parainfluenza viruses type 1 & 3. Clinical features did not vary according to underlying aetiology, the common presenting features being "decrease in general condition", cognitive and functional deterioration, and withholding of food in addition to fever and respiratory symptoms. Overall, mortality at 1 month/discharge was 9.7%. MRSA infection, low BMI, and poor function predisposed to mortality. No association between influenza vaccination status and underlying aetiology, clinical features or outcome, was observed.

Conclusions: Clinical presentation of ILI is non-specific and is mainly due to bacterial and other viral infections than influenza in the RCHE population.

Keywords: Influenza-like illness, aetiology, elderly, incidence, residential homes