Cases of COVID-19 have increased four-fold since the July 4 holiday in Los Angeles County, with the virus continuing to spread mostly among those who are not vaccinated, officials said Saturday.

The county on Saturday reported 1,827 new cases of the virus, and a testing positivity rate of 3.7%. The number of people who tested positive for the virus was near 0.5% on June 15, when the state lifted most restrictions on capacity and mandates for masking that were intended to stem the spread of COVID-19.

The rate of transmission has “rapidly increased to very concerning levels,” officials said in a statement.

Long Beach’s numbers are even more dire: On Friday, officials reported a 331% increase in average daily cases since July 4, and an 860% increase since June 15.

The city’s positivity rate is now 4.1%, with case rate of 9 per 100,000 residents. That is still well below the peak of cases, hospitalizations and deaths reported in January, but significantly above the numbers seen on June 15, when the case rate was 1.2.

The quick spread of the virus promoted city and county health officials to issue a new health order this week requiring masks indoors, regardless of a person’s vaccination status. (Long Beach’s amended health order, which goes into effect at 11:59 p.m. Saturday, can be viewed here.)

Masks will be required in all indoor public places, venues, gatherings, and businesses (including offices, retail, restaurants, theaters, family entertainment centers, meetings, and state and local government offices). Dining indoors is still allowed, and the county and city have not placed any restrictions on capacity.

Health officials attribute the quick escalation of cases to a number of factors, including intermingling among unmasked people who may or may not be vaccinated, as well as a new, more contagious strain of the virus known as the “delta variant.”

Close to one-third of eligible people over 12 have not been vaccinated against COVID-19 in Long Beach. In Los Angeles County as a whole, roughly 4 million people have not been vaccinated, including 1.3 million children under 12.

“While vaccinations are by far the most powerful tool we have, we are nowhere near herd immunity,” Barbara Ferrer, director of the county Department of Public Health, said in a statement Saturday.

For information on how to get vaccinated, click here.

What you need to know about the new mask mandate in Long Beach, LA County

Melissa Evans is the Chief Executive Officer of the Long Beach Post and Long Beach Business Journal. Reach her at [email protected], @melissaevansLBP or 562-512-6354.