In the drive to reopen Louisiana, the state and an array of medical providers have been on a push over past several weeks to increase testing for the novel coronavirus.

An increased number of tests can be expected to reveal more cases, but new data from the state show the rate of positive cases per test rose sharply over the past two weeks in East Baton Rouge Parish and other parts of the capital region.

That means for a given batch of tests, more cases are being found now than the same batch would have found two weeks ago, possibly suggestive of increased spread of the virus.

In East Baton Rouge Parish, the average weekly rate of positives per test has quadrupled over the past two weeks, rising from 2.5% to 10.3% between the week ending June 21 and the one ending Sunday, an Advocate analysis of state data shows.

On Monday, East Baton Rouge's one-day rate of cases to tests rose to 17.4%, well above the state and regional figures. 

Sometimes known as the "positivity" rate, this ratio of new cases to tests has been seen by federal and other health experts as a measure of the penetration of testing efforts, a sign of a viral spread and a marker for reopening the society.

One of the federal criteria for entering Phase 3 is that states have a positivity rate of equal to or less than 10% for 14 days.  

City-parish officials said the increasing numbers are a worrying sign of potential viral spread and underscored the need for vigilance with social distancing measures and face coverings.

"The numbers are very concerning. They tell us that people need to wear masks in public. They need to get tested and to participate in the state contact tracing program," said Mark Armstrong, city-parish spokesman. 

With the increased rates of positive tests, new cases in the parish have also been trending upward. The rolling seven-day average for new cases in East Baton Rouge has risen from 19 cases reported on June 20 to nearly 91 new cases reported on Monday. The high since the outbreak began was on May 20 when the rolling case average fell just under 104 new cases.

The rising case numbers have helped push East Baton Rouge's cumulative raw total for cases past 5,000 on Monday, hitting 5,034 since the virus was first detected in the parish in mid-March. 

Across the 12-parish Baton Rouge region, the rates of positive tests were generally on the decline in the weeks leading up and just after the state's Phase 2 easing of social distancing restrictions on June 5. Since then, however, the capital region as a whole made a similar but less sizable upward turn in average positivity rates than East Baton Rouge has.

Despite those trends, new deaths from the COVID-19 illness have fallen to their lowest levels since the outbreak began. The Baton Rouge region has also seen less of an increase than the state as whole in hospitalizations and is well off the region's high in mid-April, state health data show.

State health officials have noted that many of the rising number of cases in Louisiana are young adults who are less likely to have severe health effects from the virus, though they could pose an infection risk for their older relatives. Parish level data weren't immediately available. 

Some health experts, while concerned with the numbers in the Baton Rouge region, also cautioned against drawing too many conclusions at this point due to the relatively small window of time and limitations in state data.

Susanne Straif-Bourgeois, an epidemiologist with the LSU Health Sciences Center in New Orleans, pointed out that she recently learned the state's test counts can include those of the same person tested more than once during isolation or contact tracing efforts.

She and others added that close consideration has to be given to whether the rise in positivity rates coincides with major testing efforts of vulnerable people or those who are more likely to be infected.

Susan Hassig, a Tulane University epidemiologist, pointed out that the upward shift in East Baton Rouge roughly coincided with an outbreak of more than 100 cases among workers and patrons of the Tigerland bars in Baton Rouge earlier this month.

That discovery by heath officials led to a subsequent drive-up testing effort on Thursday of others who feared they may have also been in contact with that outbreak.

She called the latest percentages "disturbing" but worth further consideration first.

"My take on it would be 'concerned, but I want to see a few more days of more normal testing behavior to see what actually happens,'" Hassig said.


Email David J. Mitchell at dmitchell@theadvocate.com

Follow David J. Mitchell on Twitter, @NewsieDave.