More than 40% of coronavirus cases in US nursing homes are asymptomatic, new study finds
- Researchers looked at data from more than 500 nursing homes across 34 states
- A total of 40.6% of more than 5,400 positive coronavirus cases were asymptomatic with no signs such as fever, coughing or shortness of breath
- Nearly one in five cases were presymptomatic meaning they did not exhibit symptoms until after testing positive
- Nursing homes in the top 5% of counties with COVID-19 prevalence had higher counts of asymptomatic and presymptomatic patients
Nearly half of novel coronavirus cases in nursing homes may be asymptomatic, a new study suggests.
Researchers found that more than 40 percent of patients did not experience a cough, a fever or difficulty breathing.
Additionally, about one in five cases did not have symptoms of COVID-19 until after they tested positive for the virus.
The team, from Brown University School of Public Health, says the findings not only provide evidence for increased testing and isolation but also that nursing home location could be an important predictor of future outbreaks.
A new study from Brown University School of Public Health found that 40.6% of more than 5,400 COVID-19 cases across nursing homes were asymptomatic. Pictured: Workers from a Servpro disaster recovery team enter the Life Care Center in Kirkland, Washington, to begin cleaning and disinfecting, March 11
Nursing homes in the top 5% of counties with COVID-19 prevalence had higher counts of asymptomatic and presymptomatic patients (above)
Early on in the pandemic, Dr Robert Redfield, the director of the Centers for Disease Control and Prevention, estimated that one in four patients are asymptomatic.
In an interview with NPR in March, he said this probably explains how cases continued to spread across the country even as strict social distancing measures were enacted.
Redfield added that asymptomatic people can shed the virus up to 48 hours before any symptoms appear.
However, new estimates suggests that between 40 percent and 45 percent of all people infected with SARS-CoV-2 are asymptomatic when they are tested.
For the study, published in JAMA Internal Medicine, the team looked at data from Genesis HealthCare, a company with about 500 nursing homes across 34 states.
Researchers combined electronic medical records with daily infection logs to identity all positive cases recorded between March 16, 2020 and July 15, 2020.
At the end of the study period, 182 nursing homes in 20 states had at least one infection with a total of 5,403 positive cases.
Results showed found that 2,176 patients were symptomatic with signs such as a dry cough, fever, fatigue and shortness of breath.
However, 2,194 patients – or 40.6 percent – were asymptomatic, meaning they did not exhibit any of those signs.
What’s more, the remaining 10.1 percent of cases were presymptomatic, which means they did not develop symptoms until after testing positive.
Rates were slightly higher among nursing homes where facility-wide testing was conducted rather than unit-based testing, which occurs when all residents in specific units are tested without testing the whole house.
Among facility-wide testing sites, 40.9 percent of cases were asymptomatic and 19.3 percent of cases were presymptomatic.
Nursing homes in the top five percent of counties with coronavirus prevalence had higher combined counts of asymptomatic and presymptomatic cases than those in counties with a lower prevalence.
‘We observed high asymptomatic and presymptomatic SARS-CoV-2 infection rates in a large multistate sample of [nursing homes], demonstrating the importance of universal testing for identifying and isolating cases,’ the authors wrote.
‘The [nursing homes] located in areas with high SARS-CoV-2 prevalence detected higher numbers of asymptomatic and presymptomatic cases during initial point prevalence surveys, building on emerging evidence that [nursing home] location is an important predictor of outbreaks.’