If you think you may be experiencing symptoms of COVID-19, please consult your healthcare provider.
Diagnostic testing is an essential component of our national response to COVID-19. Testing is utilized to diagnose disease in symptomatic patients, screen for asymptomatic carriers, and conduct epidemiologic surveillance to assess the pandemic in order to develop and monitor the effectiveness of public health interventions.
The Role of Public Health Laboratories in COVID-19 Testing
In the US,
public health laboratories have played a vital role in the COVID-19 testing response. They were the only laboratories authorized to conduct testing outside of the US Centers for Disease Control and Prevention (CDC) until March 13, 2020. At least one public health laboratory in every state, the District of Columbia, Puerto Rico and Guam is capable of testing for COVID-19; this includes all state- level and many local and territorial public health laboratories.
Follow a COVID-19 Test at Virginia’s Public Health Laboratory
For public health laboratory COVID-19 testing data, visit the
APHL COVID-19 Capacity and Capability Dashboard.
For laboratories conducting COVID-19 testing, visit the
APHL Laboratory and Testing Resources page for more information.
Types of COVID-19 Testing and Surveillance
Molecular-based diagnostic testing is used to identify the SARS-CoV-2 virus' genetic material, ribonucleic acid (RNA). RNA remains in the body only while the virus is still replicating, so this type of testing is best suited to detect current, active infections. Most molecular tests for SARS-CoV-2 use the process of real-time reverse transcriptase quantitative polymerase chain reaction (RT-PCR).
Specimens for molecular testing should be taken from areas of the body where the virus is likely to be found, such as in the nasal passages and sputum.
Molecular testing is the type of COVID-19 test most commonly performed at public health laboratories, though many also perform serology testing.
Learn more about molecular testing.
Serology testing is used to detect the presence of SARS-CoV-2 antibodies in the blood. Antibodies are made in response to an infection, usually within one to three weeks. A positive antibody test is assumed to mean that a person has been infected with SARS-CoV-2 at some point but does not indicate whether someone is currently infected or infectious.
For this reason, serology is not an effective means of diagnosis, but may be useful for general surveillance by quantifying the total number of COVID-19 cases in a population, including asymptomatic and already-recovered individuals.
Learn more about antibody testing.
Antigen tests are immunoassays that detect the presence or absence of a specific viral antigen, which implies current viral infection. Antigen tests are used in the diagnosis of a variety of respiratory pathogens, including influenza viruses and respiratory syncytial virus.
Antigen tests for SARS-CoV-2 are currently authorized to be performed on nasopharyngeal or nasal swab specimens placed directly into the assay's extraction buffer or reagent. These tests are relatively inexpensive and offer a short turnaround time; however, currently-available SARS-CoV-2 antigen tests report significantly lower sensitivity than most molecular tests, though they do report high specificity.
Learn more about antigen testing.
Sequencing of a pathogen's DNA or RNA allows scientists to detect genomic markers and mutations of interest. Changes in a virus' genome can affect its ability to spread, susceptibility to current treatments and vaccines, and virulence. Scientists can use sequencing data to trace transmission patterns and
identify variant viruses.
Many public health laboratories are performing sequencing of COVID-19 specimens and contributing data to CDC's
SARS-CoV-2 Sequencing for Public Health Emergency Response, Epidemiology and Surveillance (SPHERES) consortium, as well as submitting viruses to CDC for sequencing and further characterization as part of the
National SARS-CoV-2 Strain Surveillance (NS3) program.
Learn more about genomic sequencing.
Testing wastewater for SARS-CoV-2 is a tool that public health officials can use to better understand community COVID-19 infection trends. Wastewater, or "sewage," includes used water from homes and other buildings that can contain fecal waste. Because SARS-CoV-2 can be shed in the feces of infected symptomatic and asymptomatic individuals, wastewater can be tested for SARS-CoV-2 RNA to provide early estimates of increasing and decreasing infection trends of the people living or working in a wastewater collection area, or "sewershed."
Learn more about wastewater surveillance.