SEVERE HUMAN RHINOVIRUS OUTBREAK ASSOCIATED WITH FATALITIES IN A LONG‐TERM CARE FACILITY IN ONTARIO, CANADA

To the Editor: Rhinovirus (HRV) infections are one of the most common causes of viral illnesses in humans. Infection of healthy adults with HRV can lead to a self‐limited upper respiratory tract illness, also known as the common cold, but it can cause more‐severe disease in elderly patients, such as exacerbations of chronic lung disease, pneumonia, and death. ¹ , ² Several reports of HRV outbreaks in elderly patients have been described. ³ , ⁴ , ⁵ , ⁶ An outbreak of rhinovirus in a long‐term care facility (LTCF) causing severe disease in the province of Ontario during the 2009 pandemic of influenza A H1N1 (pH1N1) is reported.

The LTCF involved is a 42‐bedroom, 60‐resident home located in an urban setting and staffed by 100 employees. The local Department of Public Health received notification of a respiratory outbreak on July 13, 2009. Outbreak control measures at the facility were implemented, and local physicians performed medical management. Nasopharyngeal swabs were collected and tested using reverse transcriptase polymerase chain reactin for the presence of adenovirus, influenza A/B, parainfluenzae 1 to 3, respiratory syncytial virus (RSV) A and B, rhinovirus A, and coronavirus OC43/229E/NL63 viruses using the Seeplex RV kit (Seegene USA, Rockville, MD) according to the manufacturer's instructions. In addition, standard viral and bacterial cultures, rapid antigen testing for influenza A/B and RSV, Legionella direct fluorescent antibody and culture and urine antigen, and Mycoplasma pneumoniae/Chlamydophila pneumoniae nucleic acid testing were performed.

Thirty‐two residents and 21 staff developed respiratory symptoms (attack rates of 53% and 21%, respectively). The outbreak lasted 43 days and peaked 9 days after declaration. The average age of affected residents was 87.6 (range 75–102). HRV was identified in five of 14 nasopharyngeal swabs from symptomatic residents; no other pathogens (viral or bacterial) were detected. Seven deaths occurred during this outbreak. Six fatalities were identified as due to pneumonia or respiratory infection and one due to “failure to thrive” related to a fractured femur. To determine the virus type, the 5′ UTR, VP4/VP2, and VP1 regions of HRV‐positive samples were amplified and sequenced. Nucleotide sequence showed 93% homology to HRV‐A 33 strain ATCC VR‐330 (accession number FJ445128). Sequences were deposited in GenBank database under the nucleotide sequence accession numbers GU477327, GU477328, GU477335, GU477336, GU477341, and GU477342.

HRV is increasingly recognized as capable of causing frequent or severe clinical manifestations. In a study from the United Kingdom of community‐dwelling older adults, HRV accounted for 52% of identified respiratory pathogens, with a lower‐respiratory tract clinical presentation in 64% of cases. ⁷ Several reports have documented the importance of rhinovirus infection in elderly patients, and the high mortality described here is consistent with recent published reports. ² , ⁵ , ⁶ Detection of rhinoviruses has long been a problem for clinical identification, because the extreme diversity of these viruses renders the immunofluorescence antigen detection method not useful, and the cytopathic effects associated with HRV are often spurious, rendering viral culture unreliable. ⁸ , ⁹ Moreover, because multiple serotypes exist, of retrospective serology cannot be used to evaluate the burden of HRV disease. ² As a result, a significant underestimate of the number of outbreaks and the recognition of morbidity and mortality associated with HRV is likely. Nucleic acid testing is a more‐sensitive tool than viral culture for diagnosis of HRV A and B and may be the only way to detect HRV‐C. ⁹ , ¹⁰

With sensitive nucleic acid testing methods, viruses detected from nasopharyngeal swabs may represent asymptomatic colonization or nonliving organisms, and causality must be made cautiously. Because specimens from the lower respiratory tract (e.g., bronchoscopy or autopsy) were not available it is not possible to state with certainty that rhinovirus was present in the lower respiratory tract of all fatalities, although because no other pathogens were found despite extensive microbiological investigation, it is likely that HRV was the main cause of this outbreak and related deaths. In conclusion, rhinovirus can present with severe and lethal disease and mimic other severe respiratory viral illnesses. Because this outbreak occurred temporally during the North American influenza A H1N1 pandemic, multiplex nucleic acid–based respiratory testing was the cornerstone in differentiating rhinoviruses from influenza and in steering outbreak management, antiviral use, and vaccination. Because lower respiratory tract infections are leading contributors to significant morbidity in LTCF and are due to an undetermined etiology in more than half of cases when using traditional methods such as antigen testing and viral culture, prompt diagnosis using molecular tools will be increasingly important in outbreak settings such as LTCFs.