All About Testing

There are 3 kinds of tests for SARS-CoV-2 under the FDA’s Emergency Use Authorization (EUA): Molecular, Antibody, and Antigen testing.

Molecular test — RT-PCR (Reverse transcription polymerase chain reaction): This is a molecular in vitro diagnostic test that identifies the presence of virus in the body through collection of nasopharyngeal, oropharyngeal, or other respiratory specimens by swabbing.

A false-negative result may occur if:

    • a specimen is improperly collected, transported or handled
    • inhibitors are present in the specimen
    • there are too few virus particles present in the specimen.

Detecting the presence of the virus doesn’t indicate whether or not someone is infectious.

A single negative result does not mean you can skip social distancing or stop wearing a mask.

A negative test result only means that you didn’t have COVID-19 at the time of testing. It’s possible your sample was collected too early in your infection.

You could also be exposed to COVID-19 after the test and then get infected and spread the virus to others.

If you develop symptoms later, you may need another test to determine if you are infected with the virus that causes COVID-19.

Antibody Test — Serology: Blood test with a turn-around time of typically same day, but sometimes can take a couple days. Serology is especially important because it may detect previous infections in people who had few or no symptoms.

Antibodies are proteins made by the immune system in response to a foreign substance (called an antigen). Each antibody recognizes a small portion of a single antigen (antibody specificity) so an antibody that recognizes the virus that causes chickenpox will not recognize the virus that causes measles.

There are 5 different types, or classes, of antibody: IgG, IgM, IgA, IgE, and IgD. Most rapid novel coronavirus tests look for IgG and IgM. After an infection, your body starts to produce IgM antibodies first, which can be detected after about a week and hang around for a couple weeks after your symptoms start. IgG antibodies are part of your immune system’s long-term arsenal, detected after 2 weeks from the start of symptoms, peaking around 30 days, and hang out for months or even years after you recover.

IgM antibodies: Produced first, detected ~ 1 week after start of symptoms. Because it is only detectable for a couple weeks, it is used to determine recent infection.

IgG antibodies: Produced later, detected ~ 2 weeks after start of symptoms. Because it can be detected for months or years after infection recovery , it is used to determine past infection.

cov-2-immune-response-timeline.001

In general, there are two kinds of antibody test methods: binding antibody or neutralizing antibody tests.

Binding antibody tests: These tests use purified proteins of SARS-CoV-2, not live virus, and can be performed in lower biosafety level laboratories (e.g., BSL-2).

Point-of-care (POC) tests usually use lateral flow to detect IgG, IgG and IgM, or total antibody in whole blood, serum, plasma, and/or saliva. A common example of a lateral flow device is a home pregnancy test. Some point-of-care tests can be performed on blood collected from a fingerstick rather than a blood draw.

Laboratory tests typically use ELISA (enzyme-linked immunosorbent assay) or CIA (chemiluminescent immunoassay) to detect IgG, IgM, and IgA antibodies, either individually or as total antibody.

Neutralizing antibody tests: As of July 2020, the FDA has not authorized the use of neutralization tests for SARS-CoV-2 yet.  In this test, a serum or plasma sample is infected with live virus in a test tube to determine if the antibodies are functionally capable of preventing infection.  Because this method involves the live virus, it requires a higher biosafety level (BSL-3 or BSL-2 laboratory).

Virus neutralization tests (VNT): Here, the SARS-CoV-2 virus comes from a clinical isolate or is modified for the assay. This testing must be done in a BSL-3 laboratory and can take up to 5 days.

Pseudovirus neutralization tests (pVNT): This test uses a non-SARS-CoV-2 modified virus (e.g. vesicular stomatitis virus, VSV) that has a piece of protein from SARS-CoV-2 attached to it. This testing can be performed in a BSL-2 laboratory, depending on the particular strain.

Unfortunately, just because we can detect them doesn’t automatically mean that they can provide immunity/protection from reinfection.

Antibody testing results shouldn’t be used to decide if someone can return to work. It also shouldn’t be used to group people together in settings such as schools, dormitories, and correctional facilities that increase the risk of transmission.

Antigen test — Rapid: Rapid diagnostic test with a turn-around time of less than one hour. Antigen tests look for specific proteins on the surface of the virus and can diagnose an active infection.

Unlike antibody tests that detect your immune system’s response to the virus, antigen tests detect viral proteins directly. The two major antigenic targets of of the SARS-CoV-2 virus are the spike glycoprotein (S) and the nucleocapsid phosphoprotein (N).

Depending on the complexity of the method, these tests can be performed in <30 minutes or may take a couple of hours. 


Have general questions? Comments?

Email asktheoptimisticscientist@gmail.com or comment below!

Resources/Further Reading

Interim Guidelines for COVID-19 Antibody Testing (CDC, updated 8/1/2020)

Great Video Explanation of Antibodies & Serology Tests (Beckman Coulter, 5/22/2020)

Incubation vs Infectious Period

Incubation Period: The time from when someone is infected to when symptoms develop. Based on existing evidence-based research, the incubation period of SARS-CoV-2 and other coronaviruses (e.g. MERS-CoV, SARS-CoV) ranges from 2–14 days. 50% of people will become ill 5 days after infection.

Infectious Period: The time when an infected person, who may not be showing symptoms, can transmit the virus to others. While it varies from person to person, it is typically ~ 7 days.

Begins: 

2 days before the start of signs/symptoms

Ends:

  1. 10+ days after illness onset and
  2. symptoms are improving and
  3. there has been no fever within the past 24 hours (without anti-pyretic medications).

Some immunocompromised individuals or those with severe COVID-19 may shed the virus for 20 days.

For asymptomatic individuals, it is more difficult to define their infectious period.

Surface Survival of SARS-CoV-2

Seriously, how long can this thing survive on surfaces?

In an earlier post, I referenced some preliminary research suggesting that SARS-CoV-2, the virus that causes COVID-19, can live in the air and on surfaces between several hours and several days. This work, originally released as a pre-print and recently finalized and published in the New England Journal of Medicine, found the virus is viable for up to 4 hours on copper, 24 hours on cardboard, 48 hours on stainless steel, 72 hours on plastics, and is also detectable in the air for 3 hours. 

A lot of posts present this information out of context and headlines can make it sound frightening, “SARS-CoV-2 Lives on Plastic for 72 Hours!!!” However, what’s more important is the amount of virus that’s still alive. It’s <0.1% of what the investigators started with. So, infection is theoretically possible but extremely unlikely at the levels they saw after a few days. 

Another important thing to mention lies in the experimental design of the aerosol component of the study. It has some caveats. They found that the virus can be detected in the air for 3 hours in the lab. However, in nature, respiratory droplets fall to the ground at a faster speed than the aerosols generated in their experiments. This is because the lab-generated aerosols are smaller (<5 μm) than what is produced from a cough or sneeze, so they remain in the air at face-height longer than the natural, heavier particles. It’s not a perfect comparison (though science rarely is, we just do our best). The size of these particles can affect how they move through the air and how they impact a surface. 

So, at the end of the day you’re more likely to become infected through the air if you’re next to an infected person versus a contaminated surface. Make sure you clean surfaces with disinfectant or soap – they work because they disturb the oily external layer of the virus keeping it from infecting your cells. 

Washington State Stay Home, Stay Safe 2 Week Order

Please be sure to refer to the original documents for questions or concerns relating to a specific situation.

“The less time we spend in public, the more lives we will save.”

Governor Jay Inslee

Summary

  • How Long? 3/25/20 – 4/5/20
    • Unless extended
  • You can still safely go outside as long as you remain at least six feet from each other.
  • Essential businesses can remain open if they follow specific sanitation and social distancing policies outlined by the CDC and WA public health.
  • Gatherings are banned
    • regardless of the number of people, public and private

What Does This Mean For Individuals?

You can only leave your home to do one of two things:

  • Essential activities 
    • Obtaining necessary supplies and services 
      • for family or household members and pets
      • such as groceries, food and supplies for household consumption and use
      • supplies and equipment needed to work from home
      • products necessary to maintain safety, sanitation and essential maintenance of the home or residence
    • Engaging in activities essential for the health and safety
      • of family, household members and pets
      • seeking medical or behavioral health or emergency services
      • obtaining medical supplies or medication
    • Caring for someone else
      • a family member, friend, or pet in another household or residence
      • to transport a family member, friend or their pet for essential health and safety activities
      • to obtain necessary supplies and services
    • Engaging in outdoor exercise activities
      • walking, hiking, running or biking
      • ONLY IF appropriate SOCIAL DISTANCING practices are used
  • Employment in essential business services 
    • Healthcare / Public Health sector
    • Emergency Services sector (Law Enforcement, Public Safety and First Responders, Public Works)
    • Food & Agriculture
    • Energy (Electricity, Petroleum, Natural and Propane Gas)
    • Water & Wastewater
    • Transportation & Logistics
    • Communications & Information Technology
    • Critical Manufacturing
    • Hazardous Materials
    • Financial Services
    • For more details, see the Essential Critical Infrastructure Workers list
  • Doesn’t Apply If:
    • If your home/residence becomes unsafe, you are permitted/urged to leave and stay at a safe alternate location (e.g. victims of domestic violence).
  • Doesn’t Apply If:
    • If you are an individual experiencing homelessness, but you are urged to obtain shelter, and governmental and other entities are strongly encouraged to do as much as they can to increase their capacity to help as many people as possible.

What Does This Mean for Gatherings?

Effective midnight on March 25, 2020 until midnight April 6, 2020 (unless extended beyond that date)

  • No public and private gatherings
  • Regardless of the number of people involved
  • doesn’t apply to people who are part of a single household or residential living unit.

What Does This Mean for Businesses?

All non-essential businesses in shall cease operations by midnight March 25, 2020 except for performing basic minimum operations.

All essential businesses are prohibited from operating unless they establish and implement social distancing and sanitation measures established by the United States Department of Labor’s Guidance on Preparing Workplaces for COVID-19 and the Washington State Department of Health Workplace and Employer Resources & Recommendations.

List of Links

CDC Situation Report – 60 Highlights on SARS-CoV-2

Solidarity Trial – International Study Being Organized

The first vaccine trial has begun just 60 days after the genetic sequence of the virus was shared by China. To ensure clear evidence of which treatments are most effective, WHO and its partners are organizing a large international study, called the Solidarity Trial, in many countries to compare different treatments.

WHO Health Alerts via WhatsApp

To increase access to reliable information, WHO has partnered with WhatsApp and Facebook to launch a WHO Health Alert messaging service. This service will provide the latest news and information on COVID-19, including details on symptoms and how people can protect themselves. The Health Alert service is now available in English and will be introduced in other languages next week.

To access it, send the word “hi” to the following number on WhatsApp: +41 798 931 892.

Virtual Concert Series

WHO and Global Citizen launched #TogetherAtHome, a virtual, no-contact concert series to promote physical distancing and action for global health. Chris Martin, lead singer of Coldplay, kicked it off earlier this week with a performance from his home. More Solidarity Sessions are planned to promote health, show support for people who are staying at home to protect themselves and others from COVID-19, and encourage donations to the COVID-19 Solidarity Response Fund.

Resources: SARS-CoV-2 and COVID-19

What to do if you have symptoms of coronavirus disease 2019 (COVID-19) and have not been around anyone who has been diagnosed with COVID-19

What to do if you have confirmed or suspected coronavirus disease (COVID-19)

National Institutes of Health (NIH) – Vaccine Research Efforts on Coronavirus (COVID-19)

Schools/Education – For updates on school closures and information and guidance for parents

Employment Security Department of WA State – Links and FAQs for workers and businesses affected by coronavirus

Business and Workers – Links and FAQs for workers and businesses affected by coronavirus

Retail businesses guidelines from Department of Public Health

Workplace Practices – handwashing and social distancing recommendations for employers


Have general questions? Comments?

Email asktheoptimisticscientist@gmail.com or comment below!