Welcome to the 26th installment of “Coronavirus Contextualized,” a recurring feature in which we explore some of the numbers swirling around in the time of coronavirus.
Through these stories, we hope to parse the numbers, including confirmed cases of COVID-19, people tested, number of hospitalizations and deaths, and provide some context to them. You can view the prior editions of “Coronavirus Contextualized” here.
These stories serve as a written roundup of the COVID-19 trends we kept our eyes on this week, with all graphs and charts living permanently on our COVID-19 data page, where they are updated multiple times a day with the latest numbers.
We’re continuing to take suggestions for what kind of data, graphs and trends you would like to see analyzed in future versions of this story or included in a future update of our data page. Reach out to [email protected] with any feedback.
Below, we take a look at some of the latest COVID-19 trends in Nevada, after state officials released an update to their data dashboard on Thursday that includes new data for tracking the coronavirus pandemic in Nevada.
The number of new COVID-19 cases reported each day continues to increase, as they generally have since mid-September.
An average of 588 new COVID-19 cases were reported each day over the last seven days, up from 494 last week and 452 the week before that. The recent low point before cases started increasing again was 267 on Sept. 14. At the high point this summer, on July 20, the state was seeing an average of 1,176 new cases reported each day.
Since the beginning of the pandemic, there have been 88,085 confirmed cases of COVID-19 across the state, including 4,119 reported in the last seven days. That’s up from the 3,457 cases reported in the previous seven-day period and the 3,165 cases reported in the seven-day period before that. At the peak in mid-July, 1,451 new cases were reported in a single day.
Washoe County District Health Officer Kevin Dick, during a press call this week, said that the county is continuing to see cases occurring related to workplaces, parties, household gatherings and weddings.
“Anytime that you have a group of people that are getting together, there's the risk for COVID-19 transmission,” Dick said. “When you're out and about running errands, or when you're in your workplace, there's the risk of transmission because we have so many cases in the community that are occurring right now.”
One in 35 Nevadans has tested positive for the virus since the beginning of the pandemic. The Silver State ranks 14th in the nation for COVID-19 cases per capita, down from 13th last week.
Testing and test positivity
State officials on Thursday announced an update to their data dashboard that tracks test numbers in a new way — referred to as “test encounters” — by counting the number of unique people tested each day. Measuring test encounters is considered one of the best ways to track the level of testing occurring in the community because the method de-duplicates instances in which one person receives multiple tests in the same day, which can happen if someone receives both a rapid test and a molecular PCR test at the same time.
In general, there are three ways of counting tests — individual test specimens, individual humans tested and test encounters. Each method has its pros and cons. Individual test specimens, for instance, tell the story of how many raw tests are being processed but may include duplicates, such as in the circumstance noted above. Total people tested tells you about the universe of people who have ever gotten tested for COVID-19, which is helpful when comparing those numbers to the total number of cases, since those numbers also represent positive humans, not individual positive tests.
The drawback of this method is that it doesn’t account for the fact that now, seven months into the pandemic, many people have gotten tested two, three, four or more times, possibly because of routine surveillance testing through their work. For example, the state could report that 1,000 new people were tested in a given day and 100 positive cases, which would come out to a test positivity of about 10 percent. However, maybe in reality 1,000 new people were tested and 1,000 people were repeat testers that day. That would instead make the test positivity rate 5 percent.
Testing encounters, by contrast, offer a picture of the unique humans tested each day. It accounts for people who are tested multiple times — say, over the course of many weeks — but removes the daily duplicates that occur when multiple specimens are collected at the same time.
The state, on its dashboard, is reporting these testing encounters by specimen collection date — meaning that if a test result comes in on a Monday but the sample was collected on a Friday, the test will show up on the state’s graph as having occurred on a Friday. The same is true for its confirmed case trends graph. While these graphs may not be helpful in the short term — since they’ll show a drop off in recent days because the data hasn’t come in yet — they are helpful in the long term for examining positive cases and testing trends.
Using this new methodology, the state is now using testing encounters to calculate its test positivity rate. That means that it’s taking the number of new, de-duplicated positive results each day and dividing them by the number of de-duplicated people who were tested that day. Those numbers are then released as an average calculated over a 14-day period with a seven-day lag.
All that said, as of Thursday, the state’s average test positivity rate was 8.5 percent, up from a recent low of 6.5 percent on Sept. 18.
By contrast, the seven-day average daily test positivity rate using the number of new people who tested positive total divided by the number of new people ever tested total was 16.7 percent as of Wednesday— generally continuing an upward trend since a recent low of 9.2 percent on Sept. 17.
(It was not possible to calculate the test positivity rate using the people by people method on Thursday because the number of total people tested reported by the state actually decreased. Kyra Morgan, the state’s biostatistician, said in an email that this decrease was because of “significant data clean-up” that identified some duplicate records that have now been excluded.)
A total of 745,344 people — or about one in four Nevadans — have been tested for COVID-19 and there have been 1,111,192 individual testing encounters since March.
COVID-19 deaths are significantly down from where they were at the peak in late August, but the average number of reported deaths each day over the last seven days has been slightly up in recent days.
As of Thursday, the average number of new deaths was 7.1, up from a recent low of 5.1 on Oct. 6 but significantly down from a high of 20.7 on Aug. 20. The previous low point before cases started to increase this summer was 1.9 deaths per day, reported on June 28.
A total of 1,700 COVID-19 deaths have been reported statewide since March. Nevada ranks 21st in the nation for deaths per capita, down from 20th last week.
Trends in the number of new deaths tend to lag trends in the number of new cases by about five weeks, state officials have said.
The number of people hospitalized with confirmed or suspected COVID-19 has been slightly up over the last week after a few weeks of a plateau.
Hospitalizations have generally been fluctuating between 500 and 540 over the last week, though they dipped to 486 on Wednesday, the last day for which data is available. Those numbers are higher than the previous low of 316 the state hit on May 30 before hospitalizations surged this summer but lower than the high point of 1,165 on July 31.
The Nevada Hospital Association, in a report this week, noted that the state is “continuing to face an increase in cases overall and seeing an upward trajectory of the trendlines.”
The association also noted that hospital conditions statewide “remain good” though “some individual facilities … are experiencing higher than average occupancy rates within the general wards and ICU based on other all-cause illness and injury.”
As of Wednesday, 73 percent of licensed hospital beds and 56 percent of ICU beds statewide were occupied. Those numbers were 76 percent and 60 percent, respectively, in Clark County and 67 percent and 47 percent, respectively, in Washoe County.
County by county
In its dashboard update on Thursday, the state also released a version of its county tracker — which follows counties determined to be at elevated risk for the spread of COVID-19 — that now updates on a daily basis instead of just once weekly on Mondays.
For instance, on Monday, only Washoe and Lyon counties were flagged as at elevated risk, but by Thursday, Clark and Lincoln counties had also been flagged.
Counties are considered at risk for elevated spread of COVID-19 if they meet two of the following three metrics:
- The average number of tests per day per 100,000, calculated over a 14-day period. If this number is less than 100, a county could be considered at risk.
- The case rate per 100,000, calculated by taking the number of cases diagnosed and reported over a 30-day period. If this number is greater than 200, a county could be considered at risk.
- The case rate per 100,000 and the test positivity rate, calculated over a 14-day period with a seven-day lag. If the case rate is greater than 50 and the test positivity rate is greater than 8.0 percent, a county could be considered at risk.
According to the dashboard, Washoe County continues to have the highest case rate in the state, 513 cases per 100,000 over the last 30 days, coupled with an 8.2 percent test positivity rate. Clark County has a case rate of 369 and a test positivity rate of 8.2 percent, while Lincoln and Lyon counties each have a case rate of 212 and test positivity rates of 13.1 percent and 10.2 percent, respectively.