Data from all 50 states and the District of Columbia showed a gradual, steady decline in viral transmission rates during the 8 weeks immediately preceding relaxation of physical distancing rules.
Researchers from the Massachusetts General Hospital (MGH) reported that the relaxation of statewide physical distancing measures that are designed to control the coronavirus disease 2019 (COVID-19) pandemic frequently resulted in an immediate reversal of public health gains against severe acute respiratory syndrome coronavirus 2 throughout the United States.
Data from all 50 states and the District of Columbia showed a gradual, steady decline in viral transmission rates during the 8 weeks immediately preceding relaxation of physical distancing rules. Almost immediately after rules were relaxed, most states reversed course. Further, 8 weeks after restrictions were lifted or loosened, only 9 of the 50 states and the District of Columbia still had low rates of transmission, according to the study.
Previously, investigators reported that statewide physical distancing measures were associated with a reduction in the growth rate of COVID-19 cases in the United States and a short-term reduction in COVID-19-related deaths. The team found that this reversal occurred regardless of the type of restriction, such as school closings, restaurant/bar closings, limiting public events, and limits on in-state travel.
The researchers used data from state governments and third-party sources, in addition to regression modeling, to estimate the extent to which relaxation of physical distancing measures affected control of COVID-19, expressed as a value represented by the number Rt.
"Rt is the average number of people each person with COVID-19 will infect," said senior study author Mark J. Siedner, MD, MPH, investigator in the Division of Infectious Diseases at MGH, in a press release. "The goal of every public health intervention should be to get the Rt down to less than one, because if each person on average infects less than one other person, ultimately the epidemic will be extinguished."
The data showed that Rt declined by 0.012 units per day in the 8 weeks leading up to relaxation of restrictions, with 46 of the 51 jurisdictions studied achieving a Rt below 1 while the measures were in place. After physical distancing regulations were relaxed, the transmission rate increased by an average of 0.007 units per day.
The average Rt was 1.16 after 8 weeks into the relaxation period, and only 9 of the 51 jurisdictions had Rt rates that remained below 1, according to the study authors.
"The hope was that these measures would lead to sustained changes in behavior: mask wearing and physical distancing,” Siedner said in a press release. “These data do not give us hope. Until a vaccine is available, these measures are proving to be the most effective solutions to contain epidemic hotspots."
COVID-19 transmission rebounds quickly after physical distancing rules are relaxed. EurekAlert! https://eurekalert.org/pub_releases/2020-10/mgh-ctr100520.php. Published October 5, 2020. Accessed October 13, 2020.