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The CDC released previously withheld and greatly scaled back guidance documents this week on reopening childcare programs, youth programs and camps, schools, workplaces, mass transit, and restaurants and bars.

Last week the FDA issued emergency use authorization for a new type of test that can detect SARS CoV2 called an antigen test. The EUA was issued to Quidel Corporation for its Sofia 2 SARS Antigen FIA. The test is authorized for use in high and moderate complexity laboratories and facilities certified by CLIA.

The test looks for protein fragments associated with the virus. The sample is collected with a nasal swab. It can produce a result in minutes. The antigen test is cheaper and easier but is less reliable than the nasal swab PRC test.

The new antigen test is very specific for the virus but is less sensitive than the molecular PCR tests.  In other words, there are very few false positives but there will be false negatives, meaning that negative results do not rule out infection.

Arizona needs a sprawling network of contact tracers to track and halt the spread of covid-19. Some researchers believe that an effective tracking system will require a few hundred contact tracers for a population the size of Arizona. 

Last week I wrote about how the Association of State and Territorial Health Officials had developed a free on-demand training for entry-level COVID-19 contact tracers. The course, called Making Contact: A Training for COVID-19 Contact Tracers supports ongoing public health agency efforts to prepare new contact tracers for their work of helping identify COVID-19 positive cases and those with whom they have been in close contact.

This week the Johns Hopkins Bloomberg School of Public Health unveiled a similar 5 hour online Course that’s designed teach non-public health professionals the fundamentals of contact tracing.

When new tests come out, they’re evaluated for how well they work. As tests are evaluated, you’ll often read the words sensitivity, specificy and predictive positive value. Here is a pointer about what those words mean:

Sensitivity refers to the “true positive rate.” It measures how frequently the test is positive when the person being tested actually has the disease. For example, when a test has 80% sensitivity, the test detects 80% of patients with the disease (true positives). However, 20% of patients with the disease are not detected (false negatives) by the test.

Specificity refers to the “true negative rate.” It measures how frequently the test is negative when the person being tested doesn’t have the disease. For example, when a test has 80% specificity, the test correctly reports 80% of patients without the disease as test negative (true negatives). However, 20% of patients without the disease are incorrectly identified as testing positive (false positives) by the test.

Positive Predictive Value is the measure of how likely it is that a positive test is a true positive rather than a false positive. This depends on how many people in the population being tested have had the disease. When there are very few people in the population that have had the disease, then there’s a higher chance that a positive test is a false positive. When there are many people in a population that have had the disease, then there’s a higher chance that a positive test is a true positive.

The FDA said they’ll be tightening requirements for companies that develop COVID-19 antibody tests to better regulate the frenzy of tests coming to market. The updated policy requires commercial antibody test developers to apply for Emergency Use Authorization (EUA) from the FDA with performance thresholds for specificity and sensitivity.

Previously, manufacturers of the tests could validate their own tests and bring them to market without FDA review. More than 100 antibody tests have entered the market, fueling a congressional investigation into the accuracy of tests.

FDA posted a list of antibody tests removed from the “notification list” of tests offered under the Policy for Coronavirus Disease-2019 Tests During the Public Health Emergency. FDA announced revised guidance recommending that commercial manufacturers of antibody tests submit an Emergency Use Authorization request within 10 business days from the date they notified FDA of their test validation or the date of publication of the revised policy, whichever was later.

Editorial Note: My advice for folks that believe that they may have recovered from a COVID infection and want to find out for sure is to get a blood draw serology test rather than the simple finger stick rapid test. The results are a lot more reliable. That test costs about $100. Turn around time is about 2 days.

Antibody tests have several important public health applications. High-quality serologic tests (e.g. the blood draw kind) can be used to estimate the prevalence of past viral infection or estimate the cumulative incidence of infection in a population (progress toward herd immunity).

They can help identify people that can be plasma donors. Plasma from donors with a good IgG titer can provide antibodies for infected persons that helps with their recovery. Antibody status can also help inform persons and employers who is at less risk for infection. 

Last week APHL issued a document outlining potential public health applications for antibody testing.  The statement provides an overview of serologic methods, considerations for selecting assays for seroprevalence surveys and test result interpretation, and outstanding research needs.

The U of A expanded its analysis of blood samples statewide to find out who has antibodies against the SARS CoV2 virus.  The State Legislature appropriated the $3.5M to fund the effort.

Testing sites are opening in all 15 counties tomorrow. Overall, there are 31 antibody testing sites across the state, with additional sites becoming available as needed. The specific testing site for each participant will be selected during the registration process.

Registration for health care workers and 1st responders is now available at covid19antibodytesting.arizona.edu. That site also has the most current information on the antibody testing initiative including qualifications for registering.

Most people who are infected by the virus that causes COVID-19 make antibodies within a few weeks of infection. The presence of COVID-19 antibodies in blood serum means the immune system mounted a response against the virus.

High SARS-CoV-2 Attack Rate Following Exposure at a Choir Practice — Skagit County, Washington, March 2020

MMWR / May 15, 2020 / 69(19);606–610 

Faith worship services are in the process of figuring out how to begin operations safely. CDC published an MMWR this week regarding an investigation into a SARS CoV2 choir spreading event that helps to inform the choral aspects of worship.

It underscores the importance of distancing and masks among choirs and if hymns are included in services. While it doesn’t exactly demonstrate that singing is an amplifier of the virus, it suggests that it plays a role. Important to consider as congregations begin their plans to resume services.

Also, the state issued a 1 page guidance document this week outlining some basic tips for faith based organizations.

COVID-19 Healthcare Demand Projections: Arizona

Esma Gel, Megan Jehn, Timothy Lant, Anna Muldoon, Trisalyn Nelson, Heather M Ross

The ASU Biodesign Institute team has published their most recent Arizona-specific model using a framework that ties disease surveillance with the future burden on Arizona’s healthcare system. Their framework accounts for multiple COVID-19 patient outcomes and the observed time delay in epidemiological findings following public policy decisions.

Lots to unpack here. Pay particular attention to Section 3.2 on pages 11 and 12, which runs through scenarios that simulate the policy decisions made last week. It’s challenging to put such a sophisticated analysis in to a succinct summary – but basically- the best modeling fit for the existing data trends, along with modifying transmission as a result of the expiration of the stay at home order (and without including seasonal effects- if any) puts us on a track for a big increase in cases and new hospitalizations in early June.

Not good. Let’s cross our fingers that people will for the most part behave responsibly and the chance in transmission will be less than in the model. Also, lets cross our fingers that there will be some kind of modifying seasonal effect.