Maryland is at risk of a second wave of coronavirus infections if the state reopens too quickly or without proper precautions, according to new research from Imperial College London.
The model, which has not been peer-reviewed, estimates the virus’ reproduction number, which is the average number of secondary infections caused by an infected person. Researchers said “the epidemic was waning” in Washington, D.C., and 26 states where the reproduction number dropped below 1. In Maryland and 23 states, however, the reproduction number is over 1.
Reproduction numbers below 1 signify the virus isn’t spreading as much as it could because of social distancing and other nonmedical interventions used to reduce gatherings, according to the report. The 24 states at risk of a second wave must take “caution” when “loosening current restrictions if effective additional measures are not put in place,” according to the study.
“Overall, we show that while all U.S. states have substantially reduced their reproduction numbers, we find no evidence that any state is approaching herd immunity or that its epidemic is close to over,” according to the report.
One of the researchers, Dr. Swapnil Mishra, cautioned trying to compare Maryland with other states. Mishra said in an emailed response to questions that the data is “not apples to apples given the variation in population and the start time of epidemic (and presumably a lot of other factors).”
The findings come after Maryland’s stay-at-home order was lifted May 15, which eased restrictions meant to stop the spread of the coronavirus. Gov. Larry Hogan enacted a “Safer at Home” advisory, which allows manufacturing, retail, haircuts and worship services to resume with limitations. Some counties are reopening at a lesser extent than what’s allowed under phase one of Hogan’s recovery plan.
In a statement, Hogan’s spokesman Michael Ricci wrote that state statistics continue to show hospitalizations on the decline and that other models show Maryland as having a reproduction number below 1.
“Different models have shown different things over the last few months, but we can definitively say that the steps we have taken in Maryland have successfully flattened the curve, and that the key data-driven metrics we use for the state’s recovery — hospitalizations and ICU beds — are at their lowest levels since mid-April," Ricci wrote in an email.
Mishra emailed: “While Maryland has reduced transmission significantly, the reproduction number is still slightly above one ... and with uncertainty it could be higher.”
Researchers predict the increased movement after social distancing measures are relaxed will lead to a resurgence of transmission. Factors such as rapid testing, contact tracing and behavioral precautions ― such as mask-wearing and hand-washing ― “are crucial to offset the rise of transmission associated with loosening of social distancing,” according to the report.
Imperial College acknowledged the report’s limitations, cautioning readers "to look at our scenarios as pessimistic, but illustrative of the potential risks.” Specifically, researchers wrote that their results do not account for additional interventions that may be introduced, such as mass testing, contact tracing and changing workplace or transit practices. The study’s results also do not account for behavioral changes such as increased mask-wearing.
Data problems such as underreporting and time lags can also influence the study’s findings, so researchers wrote that the "results should be interpreted as the best estimates based on current data, and are subject to change with future data consolidation.”
Even so, Imperial College’s study concluded “that very few states have conclusively controlled their epidemics.”
“Without changes in behaviour that result in reduced transmission, or interventions such as increased testing that limit transmission, new infections of COVID-19 are likely to persist, and, in the majority of states, grow,” according to the report.
Baltimore Sun reporter Phil Davis contributed to this article.