The Centers for Disease Control and Prevention (CDC) have started performing blood tests which it says will help determine if someone has been exposed to the coronavirus even without showing symptoms, a CDC spokesperson told Politico .
These serological tests, or serological surveys, are different from the nasal swabs used to diagnose active cases of Covid-19. By analyzing the blood, researchers will be able to determine if a person has developed certain antibodies in the blood, indicating that they have been infected with the virus and have recovered.
If it can be shown that a person has developed these protections against reinfection, they could potentially re-enter society – and the workforce – at a time when millions of Americans are living under the order to stay at home. them to prevent the spread of Covid-19.
These tests can also help retroactively collect data on the spread of the virus. In the absence of generalized diagnostic tests, many people who have experienced symptoms have simply been asked to stay at home without a formal diagnosis, while many others have no symptoms.
“We are just starting to test and we will find out very quickly,” Joe Bresee, deputy incident director for the CDC’s pandemic response, told reporters. “We think serum studies will be very important in understanding the true amount of infection in the community.”
According to information provided by the health journal Stat, the surveys will target three groups, in three phases: people living in hotspots of the disease, such as New York and Seattle, but who have not been diagnosed; a representative sample of people living across the country, in regions with different infection rates; and healthcare workers.
The first phase, on people living in hot spots, has already started, after the Food and Drug Administration (FDA) granted emergency clearance for the test kits on April 1.
The tests, developed by the company Cellex, consist of pricking a finger and can deliver a reading in 15 minutes. Other test manufacturers are working to roll out their own tests in the coming months.
The second phase, of the national population, will likely start this summer, and there is no timetable yet for the third phase of health workers, according to STAT.
About 80 percent of confirmed cases of Covid-19 correspond to mild to moderate symptoms, including cough, fever, and exhaustion. Many cases have no symptoms – perhaps 25 percent of cases, according to the CDC – and are therefore probably undiagnosed, but asymptomatic people can still transmit the virus to others more vulnerable to serious complications.
But because it was difficult to get diagnostic tests, people from all walks of life – those who felt perfectly healthy, those with suspected symptoms and even some with more severe symptoms – were encouraged stay at home, away from others and hospitals, where the infection can spread even faster.
Therefore, knowing more about the full extent of the disease, including the number of people who have already known and cured it, and the profile of people who have not gotten sick with the virus, could help researchers to better understand the virus and its spread.
These tests could also help authorities better prepare for a future response to a pandemic, according to Stat: “While it is known that a high percentage of people in a community were likely infected when the virus crossed during its first wave of infections, the response to a subsequent recurrence could be adapted to protect only those at high risk, for example. “
Immunity tests are not a panacea
At a time when millions of Americans are forced to stay at home to adopt “social distancing” measures, figuring out who is protected from the spread of the disease could be the first step in bringing some people back to the world.
As Umair Irfan of Vox wrote, tests can “keep the key to a return to normal.”
A person who has had the virus, recovered and developed antibodies – proteins built in the blood that help an immune system to identify and neutralize threats – may have some level of protection against future spread. This makes them much less likely to be infected or spread an infection when they touch a cart at the grocery store, prepare food, or visit a loved one, to name a few of the daily activities currently hampered by coronavirus.
It is not yet known whether antibodies to this virus correlate with immunity, as they do with other viruses, however.
But in a recent interview on The Daily Show, Dr. Anthony Fauci, America’s leading infectious disease expert, said experts who study the disease feel “really confident” that the recovered patients will be immune to Covid-19.
“If this virus acts like all the other viruses that we know of, once you are infected, heal yourself, eliminate the virus, then you will have immunity that will protect you from reinfection,” he said.
There are other open questions, such as the duration of this immunity and the possibility of re-infecting certain people. It is not yet known how this virus mutates; if its mutation patterns reflect the flu, there could be a new strain every year, for example.
Some previous research also indicates that repeated or prolonged exposure to the virus can cause more serious infections. This opens the question of whether antibodies can prevent infection with larger “doses” of the virus – for example, for hospital workers who are repeatedly exposed to the virus – or whether they are more effective in the population. general.
Without a clear way of knowing who poses a risk, who is at risk and who carries immunity, early lifting of social distancing measures would be a “nightmare scenario,” an infectious disease researcher told Vox.
The CDC has given no indication that this series of serological tests is being done to re-integrate people into the workforce. Yet these antibodies can provide a key clue to who can return to work safely. This can be especially important in releasing healthcare workers, at a time when many hospitals and clinics are facing staff shortages due to the coronavirus.
The UK has ordered 3.5 million of these tests, and Italy and Germany plan to use them to provide citizens with “certifications” that they can return to the world.
As Irfan wrote, these tests are not perfect:
Serological tests use blood serum, the liquid part of the blood, excluding cells and clotting proteins. Although SARS-CoV-2 is not usually found in the blood, an infection causes white blood cells to make antibody proteins that help the immune system identify and stop viruses, or mark cells infected for destruction.
Although these proteins can be detected in the bloodstream and in blood serum, it can take several days for these antibodies to be made after an infection. A serological test is therefore not always useful for finding an active infection – and can give a false negative, showing that someone does not have the virus when he actually does. The results of these tests may also be more difficult to interpret than the results of the most common RT-PCR tests used to diagnose Covid-19, which detect the genetic material of the virus.
Instead, these tests can be a screening tool. The researchers are also studying how antibodies could be collected to treat the current cases of Covid-19; they are studying how to use the blood plasma of recovered patients as a possible emergency treatment for current cases.
But there are many caveats, as Irfan points out. There is a shortage of necessary test equipment and personal protective equipment for medical personnel performing these tests. There are also many unknowns about how immunity to this new virus works:
To return to work safely, a patient should ensure that he has immunity and that he no longer spreads the virus. Since a serological test can only confirm the former, a patient may still need an additional RT-PCR test to establish the latter. In other words, they must test positive for immunity and negative for the virus itself.
SARS-CoV-2 is also a new virus, so researchers are unsure of the duration of immunity. The virus could mutate and render past immunity ineffective, although scientists have found that it mutates slowly, indicating that protection against a past infection is likely to be effective for some time.
Putting too much stock in immunity could also create a kind of incentive to get infected in order to develop antibodies, which would be very irresponsible during an epidemic of an infectious disease of which we are still largely unaware.
Instead, says Irfan, “the best strategy is not to get infected in the first place and to save time until researchers can develop and deploy a vaccine.”