04-17-2020, 03:03 AM
It isn't sufficient to quarantine contacts of known cases and wait for symptoms to show. Those contacts may have already infected others and may be pre-symptomatic or asymptomatic. Either you need to test those contacts, or quarantine their contacts.
For each case, contact tracing for a case wants to discover both the infector (the source of the infection) and any infectees (of the case being tracked).
In particular, suppose person A gets infected by community spread (no contact with someone with the disease) on day 1 and that A never noticess any symptoms. Now person A infects person B on day 3, and person C on day 7. Person B gets symptoms on day 8. Person C becomes infectious on day 9.
On day 9, person A is interviewed as a contact of person B and reports no symptoms. If that were the extent of the contact tracing, person C is missed and goes on to infect others.
Suppose that all contacts (even one-time) are asked to get tests.
Person A may no longer be positive by a PCR test. Hopefully, person A is also tested for IgM antibodies, which show they recently had the illness and may be an infector of B. If neither test is positive, the contact with C is missed. But if A tests as recently positive, person A's contacts should be traced. Then C may be found.
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I'm not sure whether the authorities can force person A to take either test. But, if the testing is available, A could be encouraged to take the test.
Even 2 months from now, using a manual trace & test approach, I'm not sure the authorities would encourage A to take the test if the only contact was that A and B had encountered each other in the grocery store one time.
With the contact tracing app, person A may be told (anonymously?) that they had contact with a known case. Person A may shelter-in-place and consider that is sufficient for a quarantine, without ever taking a test.
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What is the motivation for a person to take either a PCR or antibody test given that someone says they were exposed but you don't recognize any symptoms?
1) If you find that you do have the disease, you will take extra precautions to avoid giving it to someone around you.
1a) If you do have the disease, those around you can get tested so they might not spread it to others.
2) If you repeatedly take the test and get negative results, you might shorten a quarantine.
3) If there are some treatment that can be done early in the course of the disease to improve the outcome, you might do that.
4) You may wish to know early so you can get things in order (for illness or even death).
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To more quickly reduce the infection rate, tests (supporting the trace & test effort) should be free. Priority should be given for those with the most contacts in the last 2 weeks. (For instance, I have no contact with anyone but my wife. A grocery store clerk's test should get priority over my test.)
I am aware of a healthcare worker who had multiple symptoms in Texas. She was advised to go to the ER because its results came back sooner, but walked out when told it would cost $75. 5 days later, her symptoms are going away, and she doesn't have any results yet. The facility she works at (who did say they'd pay the ER once she told them about it) has been in limbo. That's going to be pretty much a wasted test.
For each case, contact tracing for a case wants to discover both the infector (the source of the infection) and any infectees (of the case being tracked).
In particular, suppose person A gets infected by community spread (no contact with someone with the disease) on day 1 and that A never noticess any symptoms. Now person A infects person B on day 3, and person C on day 7. Person B gets symptoms on day 8. Person C becomes infectious on day 9.
On day 9, person A is interviewed as a contact of person B and reports no symptoms. If that were the extent of the contact tracing, person C is missed and goes on to infect others.
Suppose that all contacts (even one-time) are asked to get tests.
Person A may no longer be positive by a PCR test. Hopefully, person A is also tested for IgM antibodies, which show they recently had the illness and may be an infector of B. If neither test is positive, the contact with C is missed. But if A tests as recently positive, person A's contacts should be traced. Then C may be found.
--------
I'm not sure whether the authorities can force person A to take either test. But, if the testing is available, A could be encouraged to take the test.
Even 2 months from now, using a manual trace & test approach, I'm not sure the authorities would encourage A to take the test if the only contact was that A and B had encountered each other in the grocery store one time.
With the contact tracing app, person A may be told (anonymously?) that they had contact with a known case. Person A may shelter-in-place and consider that is sufficient for a quarantine, without ever taking a test.
----------
What is the motivation for a person to take either a PCR or antibody test given that someone says they were exposed but you don't recognize any symptoms?
1) If you find that you do have the disease, you will take extra precautions to avoid giving it to someone around you.
1a) If you do have the disease, those around you can get tested so they might not spread it to others.
2) If you repeatedly take the test and get negative results, you might shorten a quarantine.
3) If there are some treatment that can be done early in the course of the disease to improve the outcome, you might do that.
4) You may wish to know early so you can get things in order (for illness or even death).
-----------
To more quickly reduce the infection rate, tests (supporting the trace & test effort) should be free. Priority should be given for those with the most contacts in the last 2 weeks. (For instance, I have no contact with anyone but my wife. A grocery store clerk's test should get priority over my test.)
I am aware of a healthcare worker who had multiple symptoms in Texas. She was advised to go to the ER because its results came back sooner, but walked out when told it would cost $75. 5 days later, her symptoms are going away, and she doesn't have any results yet. The facility she works at (who did say they'd pay the ER once she told them about it) has been in limbo. That's going to be pretty much a wasted test.