In 2003, the SARS virus seemingly appeared out of nowhere, spread around the globe, disrupted worldwide travel, and made healthcare facilities into viral exchange centers. This virus is a member of the coronavirus family, which, prior to 2003, were not widely considered to be a serious threat. The 2 known human coronaviruses at the time were known to cause only the common cold. Since that time, coronaviruses have moved to the top of the list of pathogens with pandemic potential; the experience with MERS coronavirus bears this out. After the discovery of the SARS virus but before the discovery of the MERS virus, 2 novel coronaviruses were found in human infections: NL63 and HKU1. The epidemiology of these 2 viruses has not been well characterized (especially in adults), and, given the importance of coronaviruses, a full understanding of their epidemiologic characteristics is needed. A new study, published in Open Forum Infectious Diseases, attempts to gauge how widespread HKU1 infection is in adults with respiratory symptoms.

In this study, Kanwar and colleagues at University Hospitals in Cleveland sampled 832 adults presenting with respiratory symptoms from February to April 2016. The samples were tested for the presence of HKU1 using a multiplex PCR device. Of the 832 samples, 4.2% were positive for a coronavirus--37% of which were HKU1. Important characteristics of HKU1-positive patients included 85% having a respiratory comorbidity (including smoking tobacco) and 38% using inhaled corticosteroids. 

Clinical features of case patients included dyspnea, cough, and rhinorrhea. Fever was less common. More than half of the patients required hospitalization, with pneumonia being present in the majority of the hospitalized. One patient died, while 2 were admitted to the ICU. Leukocytosis was present in most patients. Antibiotics were administered to the majority of patients. Coinfections with other respiratory viruses occurred in 17%.

This study provides important epidemiologic data regarding the spectrum of coronavirus infections in adults with respiratory symptoms. Such knowledge is essential for surveillance purposes, as understanding baseline rates and the spectrum of illness is crucial for detecting an aberration in the pattern, heralding a change in behavior of HKU1 or the appearance of another novel coronavirus. The study also highlights the fact that not all coronaviruses are benign, and they can confer a significant rate of hospitalization. Lastly, such studies reinforce the value of multiplex PCR viral testing in healthcare settings. Such devices provide granular pictures of viral epidemiology and can be sentinels in the early detection of outbreaks. As coronaviruses continue to be leading threats, future studies of the epidemiology of all members of this viral family will remain a needed task.

Kanwar A, Selvaraju S, Esper F. Human coronavirus (CoV)-HKU1 infection among adults in Cleveland, Ohio. Open Forum Infect Dis March 25, 2017. https://academic.oup.com/ofid/article/3090933/Human-Coronavirus-CoV-HKU1-Infection-among-Adults. Accessed April 4, 2017.