Asymptomatic Carriers May Play a Huge Part in COVID-19 Surge

January 12, 2021
Frank Diamond

Assume that everybody in a hospital setting is an asymptomatic carrier of COVID-19, two recent studies suggest.

Just when you think the numbers can’t get any worse, they do. December 2020 was the cruelest month when it came to coronavirus disease 2019 (COVID-19), that is until January 2021 came along. The United States topped 200,000 new COVID-19 infections yesterday for the seventh day in a row. In addition, the US has averaged more than 3000 COVID-19 deaths a day over the past week, according to Johns Hopkins University. Experts interviewed by Infection Control Today® warned that the public should have greatly curtailed participation in social gatherings over the holidays and that might have happened to some extent, but not to the extent needed to avoid what could become one of the most brutal winters in US history from a public health standpoint.

And experts have also been telling ICT® for a long time that asymptomatic carriers of the disease make it particularly difficult to control. Linda Spaulding RN, BC, CIC, CHEC, warned her fellow infection preventionists back in April 2020, that they might become unknowing carriers of SARS-CoV-2 who “could possibly give it to our co-workers and everybody we’re around and we’re never going to know we’re an asymptomatic carrier.”

The role of asymptomatic carriers continues to be explored in two recent studies in the American Journal of Infection Control. In one pre-print study, investigators with the University of Louisville found that 37% of patients presenting at a hospital are asymptomatic carriers of SARS-CoV-2. “The proportion of asymptomatic patients admitted with SARS-CoV-2 was significant,” the study concludes. “Identifying and isolating asymptomatic patients likely prevented exposure and development of hospital-acquired COVID-19 cases among healthcare workers and other patients, supporting the universal surveillance of all admitted patients.”

In the other study, investigators with Universidad Autónoma de Zacatecas in Zacatecas, Mexico found that “thirty-four (42%) contacts in the study were positive for SARS-CoV-2. Twenty-three (67.6%) manifested less than 2 respiratory symptoms, and 5 (14.7%) remained asymptomatic,” the study states. “The average of positive contacts by index COVID-19 case (R0) was 4.3 and the mean of time of positive COVID-19 test at sampling time was 18.9 days. Positive antibody test against SARS-CoV-2 was observed in 16% of the participants.”

In the study by the University of Louisville investigators, data were collected from patients who tested positive for COVID-19 and who were admitted from April 9 to July 1, 2020 to UofL Health, an acute care hospital in Louisville.

“All patients admitted to the hospital with positive SARS-CoV-2 RT-PCR tests were identified,” the study states. “The patients who had COVID-19 symptoms on admission were analyzed separately from those who were asymptomatic.”

Of the 103 patients who tested positive for the coronavirus, 65 were symptomatic, while 38 were 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,” the study states.

Assume that everybody in a hospital setting might be an asymptomatic carrier of COVID-19, which will better protect not only patients, but infection preventionists and other healthcare workers as well.

“An important strategy to protect healthcare workers and other patients is to perform a surveillance test on all patients admitted to the hospital,” the study by the University of Louisville investigators states. “In addition to surveillance testing for SARS-CoV-2, other strategies utilized were standard and transmission-based precautions, as well as universal masking of all staff.”

Investigators with the Universidad Autónoma de Zacatecas found that respiratory symptoms alone might not be enough of an indicator to identify those infected with COVID-19. “The proportion of close contacts of COVID-19 patients infected with SARS-CoV-2 (42%) and with less than 2 or with no respiratory symptoms (82.4%) was high in the study population,” the study concludes. “A low proportion of COVID-19 patients had a positive test for antibodies against SARS-CoV-2. The screening for SARS-CoV-2 in close contacts of COVID-19 positive patients should be encouraged to avoid spreading the infection and the expansion of the disease.”

Investigators examined data collected from 100 patients from June to July 2020. They found that 34 of the subjects tested positive for COVID-19, and of that 34, 23 exhibited fewer than 2 respiratory symptoms, while 5 were asymptomatic.

“The proportion of close contacts of COVID-19 patients infected with SARS-CoV-2 (42%) and with less than 2 or with no respiratory symptoms (82.4%) was high in the study population,” the study concludes. “A low proportion of COVID-19 patients had a positive test for antibodies against SARS-CoV-2. The screening for SARS-CoV-2 in close contacts of COVID-19 positive patients should be encouraged to avoid spreading the infection and the expansion of the disease.”