The U.S. government is fighting to contain and slow down the spread of the coronavirus. Testing is central to these efforts. Molecular biologist and viral researcher Maureen Ferran answers some basic questions about how these diagnostic tests work—and if there are enough to go around.

Who gets tested for the virus?

Currently there are two main reasons someone would be tested for the coronavirus: having symptoms or exposure to an infected person.

The main symptoms of COVID-19, the disease caused by the coronavirus SARS-CoV-2, are fever, dry cough, and shortness of breath. These look a lot like the flu and the common cold, so it takes a physician to determine if testing for the virus is necessary.

Initially, the Centers for Disease Control and Prevention recommended testing only people with symptoms and who had potentially been exposed to the virus. But to the surprise of public health officials, several of the first people in the U.S. who tested positive for the virus had no obvious exposure. This development suggested that the virus was being transmitted locally, meaning it was spreading from person to person easily and/or that people may have been transmitting the virus without experiencing serious symptoms.

[Photo: Governor Tom Wolf/Flickr]

How does the test work?

While collecting a sample is easy, actually determining whether a person is infected with the coronavirus is much more complicated. The current method looks for the virus's genetic material (RNA) in a patient's cells.

In order to detect the presence of RNA in the patient's sample, labs perform a test called reverse-transcription polymerase chain reaction. This method first converts any viral RNA to DNA. Then the DNA is replicated millions of times until there are enough copies to detect using a specialized piece of equipment called a quantitative PCR instrument.

If genetic material from the virus is found in the sample, then the patient is infected with the virus.

As pressure on the federal government to make tests available increased, the FDA announced a new policy on Feb. 29 that made it easier for commercial and academic laboratories to develop their own tests and allowed other certified labs to test patient samples.

Integrated DNA Technologies, a CDC contractor, shipped 700,000 tests to commercial, academic, and healthcare laboratories on March 6. Quest Diagnostics and LabCorp, two large commercial test manufacturers, started making their own test kits, which became available on March 9. Many companies, hospitals, and other institutions are now racing to develop more tests to diagnose COVID-19.

On March 10, Alex Azar, secretary of Health and Human Services, announced that 2.1 million testing kits are now available and more than one million have shipped to certified labs for testing. Millions more are expected to ship out this week.

Does everyone really need to be tested?

Realistically, it isn't feasible to test everyone who is sick in the U.S. Therefore, most health officials believe it is important to prioritize the testing of people who need it the most: those at high risk such as healthcare workers who have been in contact with COVID-19 patients; symptomatic people in areas with high infection rates; and people 65 years of age and older with chronic health issues, such as heart disease, lung disease, or diabetes. As more tests become available, it will be possible to test more people.

There's also a need to develop faster tests that do not require special equipment and personnel. Testing allows experts to better understand how the outbreak is progressing and try to predict the impact the virus will have on society.

As with all outbreaks, this pandemic will end. In the meantime, however, people need to wash their hands and try to minimize their risk of exposure. There is much to be learned about this novel coronavirus. Only time will tell if it disappears from the human population, as SARS did in 2004, or becomes a seasonal disease like flu.

The Conversation