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The Burden of Coronavirus

By Amesh A. Adalja, MD, FACP, September 27, 2013

With all of the attention paid to emerging coronaviruses—first SARS, now MERS—it may be easy to lose sight of the serious respiratory illness that can be caused by the more “ordinary” of these viruses. In addition to the MERS-CoV and SARS-CoV, 4 other coronaviruses infect humans. Two (229E, OC43) have been known as human pathogens for decades, and 2 (NL63, HKU1) were discovered in the post-SARS environment of heightened attention to this family of viruses. Generally, the non-MERS, non-SARS CoVs are considered to be responsible for a large proportion of common colds. Severe disease requiring hospitalization is rare in patients who are not immunosuppressed.

4 Winters, 400 CoV Infections

In a paper recently published in the Journal of Infectious Diseases, Walsh and colleagues report the results of a study conducted during 4 consecutive winters (1999-2003) in Rochester, New York. Using both PCR and serology, the researchers sought to quantify prevalence of the 229E and OC43 strains of C0V in seasonal respiratory infections among inpatients and outpatients.

The outpatient cohorts included 611 healthy elderly adults, 537 adults with cardiopulmonary disease, and 291 healthy young adults; the inpatient cohort included 1,388 adults hospitalized with acute respiratory illnesses.

The researchers identified 398 infections with either OC43 or 229E and 4 cases in which patients were infected with both strains. Rates of detection fluctuated throughout the study, ranging from a low of 0.5% in the healthy elderly adult cohort to a high of 15% in the young adult cohort. The highest rates of infections occurred during the winter of 2000-2001. Asymptomatic infection—serologic response without respiratory symptoms—was fairly common. Across all cohorts, 35% of infections with 229E and 18% with OC43 were asymptomatic.

As expected of the symptomatic outpatient cohorts, cough and congestion were the predominant symptoms, with rhinorrhea nearly universal. Fever and oxygen saturations below 90% were not present. Patients reported approximately 10 days of illness, including one day of being housebound. Those infected with OC43 utilized significantly more cough suppressants than those infected with 229E. Antipyretics were used equally by the various groups. People infected with the OC43 were more likely to seek healthcare.

Among hospitalized patients, 96 CoV infections were identified, 25% of which occurred in patients who were also infected with an additional virus, such as RSV or hMPV. Co-infections were more common with 229E. Pneumonia and acute exacerbation of COPD were the most common admission diagnoses. As in the outpatient cohort, a trend for more severe disease was noted in those infected with OC43, and those patients were significantly more likely to have radiographic evidence of pneumonia. Hospitalization lasted about 6 days for those infected with 229E and 9 days for those infected with OC43, with 15% of OC43 patients requiring an ICU stay as compared with just 3% in the 229E group. Three patients died.

Tracking Coronaviruses

The study by Walsh and colleagues is important because it quantifies and describes the burden of the 2 classic CoV strains during winter respiratory virus seasons. As specific viral diagnostics for CoV infection are not readily available in most institutions, diagnosis relies on clinicians’ recognition of signs and symptoms, and understanding the spectrum of illness for the various CoVs is essential to preparedness. This is particularly important given the study’s most interesting finding—the greater severity of disease caused by OC43, which led to ICU-level care for 15% of hospitalized patients infected with that strain. That familial trait is reminiscent of MERS and SARS.


Walsh EE, Shin JH, Falsey AR. Clinical impact of human coronaviruses 229E and OC43 infection in diverse adult populations. J Infect Dis 2013; epub ahead of print September 17, 2013. Accessed September 23, 2013.