Universal Surveillance for COVID-19 Works for 1 Hospital

Test all patients who go to a hospital for COVID-19, even those who do not exhibit symptoms and are there for other medical reasons. It is very possible that more than one-third of patients not there for COVID-19 will be asymptomatic carriers of the virus who may endanger health care workers and other patients, according to a study in the American Journal of Infection Control.¹

“The proportion of asymptomatic patients admitted with SARS-CoV-2 was significant,” investigators with the University of Louisville in Kentucky reported. “Identifying and isolating asymptomatic patients likely prevented exposure and development of hospital-acquired COVID-19 cases among health care workers and other patients, supporting the universal surveillance of all admitted patients.”

Investigators reached this conclusion even while acknowledging that such an approach can present logistical and financial hurdles including an increase in the cost of testing and use of the laboratory. Universal surveillance was instituted at the University of Louisville Hospital last April. The data were collected on patients from April 9, 2020, to July 1, 2020. Those who tested positive for COVID-19 were divided into symptomatic or asymptomatic categories, using the 11 symptoms that the Centers for Disease Control and Prevention says should be watched for.²

After reviewing 2882 COVID-19 tests, investigators found that 103 individuals tested positive for the disease, with 65 (63%) exhibiting symptoms and 38 (37%) considered asymptomatic. “The proportion of SARS-CoV-2 patients who were asymptomatic varied over the duration of the study but trended up from 20% at the onset of the study period to 60% at the end,” investigators wrote.

Forest W. Arnold, DO, MSc, the study’s corresponding author and an associate professor in the Division of Infectious Diseases at the University of Louisville, tells Infection Control Today® that a possible reason for this is that “there was much less travel early, during the national quarantine, but later people got out more and thus hurt themselves in car wrecks or once they got to where they were going—to work or whatever. Traveling not only put them at risk for trauma, but also for acquiring COVID-19.”

Investigators concluded that asymptomatic carriers increased the duration of the pandemic. “The reason that we currently isolate asymptomatic and symptomatic SARS-CoV-2 patients in the hospital is based on the indirect finding that they shed live virus,” the study states. “Thus, the premise of isolating asymptomatic positive patients is to contain the shedding of live virus.”

The most common reasons for admitting asymptomatic patients were trauma or childbirth. Investigators also found some socioeconomic factors involved.

“Known risk factors for COVID-19 include persons frequently in congregate settings with an increased likelihood of close contact,” the study states. “The risk factors were exemplified in our population as pregnancy, poverty, and crowding. These clusters represented a group of pregnant Hispanic patients from one area, and additional clusters of both symptomatic and asymptomatic patients in densely populated urban parts of [Louisville]. This type of information could contribute to outbreak investigations by a health department.”

References:

1. Arnold FW, Bishop S, Oppy L, Scott L, Stevenson G. Surveillance testing reveals a significant proportion of hospitalized patients with SARS-CoV-2 are asymptomatic. Am J Infect Control. 2021;49(3):281-285. doi:10.1016/j.ajic.2021.01.005
2. Symptoms of coronavirus. Centers for Disease Control and Prevention. Updated February 22, 2021. Accessed March 10, 2021. https://www.cdc.gov/coronavirus/2019-ncov/symptoms-testing/symptoms.html