Why are so many Central Valley counties stuck in the 'purple tier'?

FRESNO, Calif. (KFSN) -- Merced County is now in the less restrictive 'red tier.'

RELATED: Merced County moves into 'red tier' of California's reopening system

Some nonessential businesses can open once again indoors, as case counts and positivity rates drop.

While the progress is met with excitement, the Director of Public Health says now is not the time to ease up -- we still have a long road ahead.

"We are not seeing the end of the tunnel," said Rebecca Nanyonjo-Kemp, Merced County Health Director. "We will not be seeing the end of the tunnel for the next six to eight-month period minimum."

As Merced County joins Fresno and Mariposa counties in less restrictive tiers, other counties in Central California seem to find themselves stuck.

In order to move down from the purple or "widespread" tier to the less restrictive red "substantial" tier, there must be fewer than seven new cases per day per 100,000 residents.

Also, less than 8% of tests need to come back positive.

In Madera County, the biggest struggle comes in the form of case rates.

Currently, they're averaging about 8 a day per 100,000 residents, putting them just under the red tier.

"One person might get it at work or traveling, and then they are in the house of five or seven people and two or three others will get it so that always bumps our numbers up, making it hard to move up and meet the criteria from the state," said Dr. Simon Paul, Madera County Public Health Officer.

Tulare County faces an even tougher battle when it comes to this metric.

At the moment, they're averaging about 10 cases per day per 100,000 residents.

"We implore the people of Tulare County in order for us to lift the restrictions on our businesses, to get all of our schools back open for in-person learning, we are asking everybody to do your part,' said Carrie Montiero with the Tulare County Health and Human Services Agency.

A third metric, health equity, was recently introduced.

It requires counties to reduce positivity rates for the poorest 25% of the county.

Tulare County health officials have already met this goal, but continue to provide free testing for those living in underserved areas.

"Tulare County will continue to coordinate these pop-up mobile testing sites to provide those opportunities for individuals in those communities who may not have the means to get to their health care provider or to one of our community testing sites," she said.

Meanwhile, Kings County is inching closer to the red tier.

This week, their numbers have fallen substantially, to 3.8 cases per day and 3% positivity rate.

If the numbers hold steady for one more week, they will see the restrictions ease.