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BACKGROUND: Human coronaviruses (CoV) are endemic globally and, although typically associated with self-limited upper respiratory illness, severe illness has been associated. The Severe Acute Respiratory Syndrome (SARS) CoV was identified in 2003, and Middle East Respiratory Syndrome (MERS) CoV in 2012 causing substantial morbidity and mortality. Nevertheless, CoVs are not incorporated into routine surveillance. Through the Influenza Incidence Surveillance Project (IISP), the Minnesota Department of Health established routine testing for CoV and here we describe the characteristics of medically-attended influenza-like illness (ILI) patients with CoV detection.
METHODS: The IISP’s Minnesota site conducted surveillance from August 2010 to July 2013, defining seasons as August through July of each year. Respiratory specimens from the first 10 patients presenting with ILI (defined as fever with cough or sore throat) and the first 10 with acute respiratory infection (ARI, defined as >2 respiratory symptoms without meeting the ILI definition) each week were collected from six outpatient clinics and tested for influenza, respiratory syncytial virus, parainfluenza viruses, human metapneumovirus, adenovirus, rhinovirus, and CoV types OC43, NL63, 229E, and HKU1 by real-time polymerase chain reaction. Demographic and clinical information were collected.
RESULTS: From a combined 3,528 ARI and ILI specimens, 234 (7%) were positive for CoV, including 125 (53%) positive for OC43, 57 (24%) positive for NL63, 33 (14%) positive for 229E, and 21 (9%) positive for HKU1. Each type of CoV was detected in all years of surveillance and demonstrated temporal, but inconsistent circulation patterns. Detection of types OC43 and NL63 were highest in the fall and winter months of the 2010-11 and 2012-13 seasons, but highest in the spring months of the 2011-12 season. Types 229E and HKU1 had less discernable seasonality but were more prevalent during the 2011-12 season. Symptoms reported by CoV-positive patients included cough (79%), sore throat (70%), fever (44%), rhinorrhea (27%), myalgia (24%), malaise (22%), coryza (19%), chills (12%), and anorexia (5%). In 27% of CoV-positive specimens, at least one additional virus was detected. The average age of patients with a CoV detection was 22 years and did not differ significantly from CoV-negative patients; however, the average age of patients decreased with the number of pathogens detected (2 pathogens, 14 years; 3 pathogens, 2 years).
CONCLUSIONS: Coronaviruses were detected among 7% of outpatients with respiratory illness, and with a variable but seasonal pattern. Projects that investigate CoV over several years, such as IISP, are needed to better define prevalence, symptomatology, and circulation patterns.