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Cycle thresholds, survival rates, flu cases, negative tests – let’s address some issues

We get a lot of questions through emails and phone calls. We try to answer all of them. Sometimes common questions arise as themes. Here’s a look at some we’ve seen recently and answers from our team of public health experts.

What is cycle threshold and why does it matter?

Some people want to know the cycle threshold of our confirmed COVID-19 cases.

The most common test for COVID-19 is a PCR test. The PCR machine puts a person’s nasal swab sample through a series of cycles in search of COVID-19 genetic material, known as RNA. Each cycle amplifies any present RNA. The CT value equals the total number of cycles required to find RNA, and each positive test has its own CT value. If no RNA is found within 37 to 40 cycles, the test is negative.

So, a low CT value equals more COVID-19 genetic material. A high CT value means less.

Labs currently do not report CT values of positive test. A positive is a positive. But we get questions and comments from residents who want more information about  CT value, to shed light on how contagious a person might be or who might be more at risk for serious health issues. 

The same sample can give different CT values on different machines. And different swabs from one person can give different results. It is not a standardized measure and  not an absolute. While many see promise in gaining more information from them, members of the College of American Pathologists have urged caution in interpreting CT values.

Locally, labs don’t report cycle threshold values to us, so we do not have this data to report. We report the total number of new confirmed cases, and many  other metrics  to help people understand the spread of COVID-19 in our community.

Are we counting flu cases as COVID? Why are flu cases so low?

No, we do not count flu cases in our COVID-19 cases. If you read the above information on cycle threshold, you know a positive test only detects the specific genetic material of COVID-19. Neither flu nor cold produce positive test results. We track the flu separately.

As for flu cases, we’re early in the season and numbers remain low. We expect them to remain low because of COVID-19 precautions and an above average number of people getting flu shots. Last flu season (October 2019-April 2020), 14 people, including 2 children, died of flu.

What’s the COVID-19 survival rate?

We know survival rates for COVID-19 are high. We also know COVID-19 kills people. It’s played a part in more than 260,000 deaths in the United States and is currently killing more than 2,000 per day in this country. Many quickly point to 99% survival rate. That’s already decreasing if you look at the basic math of the national formula. And it’s currently killed more than 225 of our Pierce County family, friends and neighbors.

Regardless of percentages, the more positive cases, the more chances deaths will continue. More families will lose loved ones. And is surviving COVID-19 the same as fully recovering? It will be quite some time before we understand the full picture of COVID’s lingering effects, but we are seeing reports of heart and lung damage, strokes, seizures and other brain issues, blood clots and vessel problems, and issues with fatigue and mood changes.

Stopping the spread, and deaths along with it, requires everyone to do their part – mask up, keep a safe distance from others, wash your hands and avoid gatherings.

 My test was negative. Am I safe to travel or to see friends or family?

Not necessarily. If you had been exposed to COVID-19 without knowing, a negative test could mean that, on the day of your test, the virus had not replicated inside your body enough to produce a positive result. It does not mean you are clear of COVID-19 after a possible exposure. Only a negative test following a 14-day quarantine would guarantee you are free of COVID-19.