COVID-19 transmission is now 'substantial' across Delaware. We tell you how to stay safe.

A week after the Centers for Disease Control and Prevention revised its mask-wearing recommendations, Delaware is seeing "substantial" COVID-19 transmission across the state.

Under the federal agency's recommendation, everyone in Delaware – vaccinated and unvaccinated – should wear a mask in public indoor spaces. The recommendation applies to every county in the country with a seven-day case rate per 100,000 residents greater than 50.

A week ago, only Sussex County qualified. By Monday, all three counties had "substantial" spread, with New Castle County close to passing Sussex County in case rate per capita.

Statewide, the spread of COVID-19 has worsened dramatically over the past several weeks due, in part, to the emergence of the delta variant, officials and health experts say.

The delta variant is more transmissible than previous strains of the virus and could be more dangerous. It could also more easily spread from vaccinated people, according to CDC data published Friday.

According to state data, 99% of cases in Delaware have been in people not fully vaccinated.

Over the past two weeks, Delaware's seven-day case average has increased 149% to 115.6. It's Delaware's highest case rate since May 18.

Hospitalization and death rates have remained low compared with surges earlier in the pandemic. On Monday, 40 people were hospitalized in Delaware with COVID-19. The state reported five COVID-19 deaths in July.

Leaders in several states have recently issued masking recommendations, reinstated mask mandates or implemented other mitigation measures in response to the rise of the delta variant.

There's also been a push – led by President Joe Biden's new requirement that all federal employees must be vaccinated or get tested regularly – to have more employers mandate COVID-19 vaccinations.

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Delaware Gov. John Carney has not announced any changes to Delaware's approach since the CDC shared its new recommendations last week. Throughout the pandemic, Delaware has almost always followed the CDC's guidance.

Pennsylvania, New Jersey and New York officials last week stopped short of reinstating statewide mask mandates, but encouraged people to follow the CDC recommendations.

New York Gov. Andrew Cuomo has taken the most action of the governors in the region. Cuomo on Monday said private businesses in his state, including stadiums and restaurants, should switch to "vaccine-only admission," requiring staff and customers to be vaccinated to enter. All New York state and city employees, as well as all Metropolitan Transportation Authority and Port Authority workers, must be vaccinated.

All New Jersey health care workers, along with those who work at state prisons and county jails, will be required to get vaccinated or get tested regularly, Gov. Phil Murphy announced Monday.

White House press secretary Jen Psaki on Monday said that a nationwide vaccination requirement "is not on the table," but employers have the right to institute their own rules.

ChristianaCare last week became the largest employer in Delaware to require employees to be vaccinated. It's the second health care system in Delaware to mandate vaccinations for employees, joining Saint Francis Healthcare.

About 6 in 10 Delawareans (70.6% of the 12 and older population) have received at least one dose of the COVID-19 vaccine, according to CDC data.

State officials are still encouraging Delawareans to get vaccinated, especially  the emergence of the delta variant.

The pace of vaccinations in Delaware increased the week following the announcement of the new CDC guidance. Last week, about 835 people per day received their first dose of the Pfizer or Moderna vaccines, up from 701 the week prior.

Contact Brandon Holveck at bholveck@delawareonline.com. Follow him on Twitter @holveck_brandon.