# Do false negatives imply low viral load? **URL:** \ **Category:** The Quarantine Zone\ **Tags:** covid-quarantine\ **Created:** [July 16, 2020, 4:27am UTC](https://boards.straightdope.com/t/do-false-negatives-imply-low-viral-load/915461 "2020-07-16T04:27:38Z")\ **Posts on this page:** 10\ **Page:** 1
**Author:** ![RealityCheck71](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/realitycheck71/32/3493_2.png) [@RealityCheck71](https://boards.straightdope.com/u/RealityCheck71)\ **Post date:** [July 16, 2020, 4:27am UTC](https://boards.straightdope.com/t/do-false-negatives-imply-low-viral-load/915461/1 "2020-07-16T04:27:38Z")
… in active infection testing? By that I mean, is that the main source of the errors (or much of one at all) I’m sure there’s some handling/procedure produced errors. What else? ---
**Author:** ![Tfletch1](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tfletch1/32/5340_2.png) [@Tfletch1](https://boards.straightdope.com/u/Tfletch1)\ **Post date:** [July 16, 2020, 4:34am UTC](https://boards.straightdope.com/t/do-false-negatives-imply-low-viral-load/915461/2 "2020-07-16T04:34:20Z")
Yes, viral load is one. Degraded specimen, especially if it’s testing for an RNA virus. RT-PCR tests are looking for the RNA. I suppose bad test reagents but that should be picked up with the positive control. ---
**Author:** ![RealityCheck71](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/realitycheck71/32/3493_2.png) [@RealityCheck71](https://boards.straightdope.com/u/RealityCheck71)\ **Post date:** [July 16, 2020, 5:13am UTC](https://boards.straightdope.com/t/do-false-negatives-imply-low-viral-load/915461/3 "2020-07-16T05:13:08Z")
But with the current better tests, is that the major reason? I’m just curious bcause that would also imply false negatives were less contagious. ---
**Author:** ![Tfletch1](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tfletch1/32/5340_2.png) [@Tfletch1](https://boards.straightdope.com/u/Tfletch1)\ **Post date:** [July 17, 2020, 3:13am UTC](https://boards.straightdope.com/t/do-false-negatives-imply-low-viral-load/915461/4 "2020-07-17T03:13:17Z")
I suppose that depends. If someone tests because they think they were exposed but are several days before they start showing symptoms, their viral load is low and they may not be that contagious. Also, viral load slowly drops a little over a week after symptoms start. Sometimes the tests will come out negative and it’s harder to culture live virus. So they may be less contagious but if they’re coughing a lot, they’re spewing particles all over. ---
**Author:** ![RealityCheck71](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/realitycheck71/32/3493_2.png) [@RealityCheck71](https://boards.straightdope.com/u/RealityCheck71)\ **Post date:** [July 17, 2020, 3:38am UTC](https://boards.straightdope.com/t/do-false-negatives-imply-low-viral-load/915461/5 "2020-07-17T03:38:15Z")
Well, what I’m thinking about is nursing home negative test “passports” for family visitors. Some might say that’s a bad idea because of the high false negative rate. If the vast majority of false negatives were still likely not contagious at test time, it would make those passports a safer idea. ---
**Author:** ![Tfletch1](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tfletch1/32/5340_2.png) [@Tfletch1](https://boards.straightdope.com/u/Tfletch1)\ **Post date:** [July 17, 2020, 2:16pm UTC](https://boards.straightdope.com/t/do-false-negatives-imply-low-viral-load/915461/6 "2020-07-17T14:16:54Z")
> [@RealityCheck71](#): > > Well, what I’m thinking about is nursing home negative test “passports” for family visitors. Some might say that’s a bad idea because of the high false negative rate. I definitely think it’s a bad idea. ---
**Author:** ![RealityCheck71](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/realitycheck71/32/3493_2.png) [@RealityCheck71](https://boards.straightdope.com/u/RealityCheck71)\ **Post date:** [July 17, 2020, 2:21pm UTC](https://boards.straightdope.com/t/do-false-negatives-imply-low-viral-load/915461/7 "2020-07-17T14:21:11Z")
They’ve already been doing it up here for around a month. These residents have been basically locked in a room for months with no visitors. ---
**Author:** ![RealityCheck71](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/realitycheck71/32/3493_2.png) [@RealityCheck71](https://boards.straightdope.com/u/RealityCheck71)\ **Post date:** [July 17, 2020, 2:27pm UTC](https://boards.straightdope.com/t/do-false-negatives-imply-low-viral-load/915461/8 "2020-07-17T14:27:41Z")
> **[Family members line up for COVID-19 tests as care home visit rules change |...](https://www.cbc.ca/news/canada/ottawa/family-members-line-up-for-covid-19-tests-as-care-home-visit-rules-change-1.5617713)** > > Ottawans with loved ones in long-term care homes streamed in for COVID-19 tests Thursday in order to comply with new requirements that finally allow visits at those facilities. ---
**Author:** ![Tfletch1](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tfletch1/32/5340_2.png) [@Tfletch1](https://boards.straightdope.com/u/Tfletch1)\ **Post date:** [July 17, 2020, 2:45pm UTC](https://boards.straightdope.com/t/do-false-negatives-imply-low-viral-load/915461/9 "2020-07-17T14:45:16Z")
Oh, I forgot you’re in Canada. I wouldn’t worry about it. The tests are an extra precaution, but you all don’t have nearly the number of cases. What’s the probability of having a presymptomatic person where cases are already low? ---
**Author:** ![RealityCheck71](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/realitycheck71/32/3493_2.png) [@RealityCheck71](https://boards.straightdope.com/u/RealityCheck71)\ **Post date:** [July 17, 2020, 2:54pm UTC](https://boards.straightdope.com/t/do-false-negatives-imply-low-viral-load/915461/10 "2020-07-17T14:54:48Z")
Yes but we botched our nursing care covid response so extra precautions are good. I’m not really worried about it – I’m curious about whether a false negative probably means “not very contagious”