Researchers at Marshfield Clinic Research Institute have found that over half the people who lived in the same household as someone with COVID-19 tested positive for the virus.​

The study was conducted by researchers at the Center for Clinical Epidemiology and Population Health and Integrated Research and Development Laboratory at the Research Institute in collaboration with investigators at Vanderbilt University Medical Center and the Centers for Disease Control and Prevention (CDC).

The CDC recommends those that have tested positive for or are expected to have COVID-19 should self-isolate at home using a separate bedroom and bathroom. Masks also should be worn in shared spaces in the house.

"A lot of people don't have immunity to the virus. Think about household dynamics. If you're in close contact with your family members it's likely you'll get the virus," said Huong McLean, Ph.D., M.P.H., research scientist with the Center and principal investigator on the study at the Research Institute.

The study aimed to estimate how often transmission occurs in households and identifies factors associated with transmission. Families were followed daily for 14 days by reporting symptoms and contact patterns. They also provided samples to test for SARS-CoV-2, the virus that causes COVID-19.

The study found that of the 191 participants that did not have any symptoms on the day the family member that tested positive began experiencing symptoms, 53% tested positive for the virus that causes COVID-19.

It was estimated that about 75% of COVID-19 infections were identified within five days of when the family member that tested positive began developing symptoms. This shows that COVID-19 can spread rapidly within households. The study also showed that COVID-19 can originate from both children and adults.

“We were excited to be able to deliver these results quickly," Dr. McLean said. “It took considerable effort from the team to get this study started and keep it going. We sincerely appreciated everyone that participated in this important study."

The study was a modification of an influenza household transmission study that has been conducted by the Center for the past three influenza seasons. Both studies were funded by the CDC and will be enrolling households through this coming influenza season.​