Fact check: Positive coronavirus test followed by negative antibody test is not proof the virus is a lie

A Facebook post showing results of a positive coronavirus test and negative antibody test has been misleadingly used to question the veracity of the disease.

Reuters Fact Check. REUTERS

The post, originally uploaded on October 4 (here) and reshared in a screenshot two days later (here), has been shared nearly 2,000 times. Included in the posts are two screenshots showing emails from Britain’s National Health Service (NHS) . The first, from Sept. 5, confirms the Facebook user has tested positive for the coronavirus. The second, from Sept. 30, says the same user tested negative for virus antibodies. These two tests are distinct, as explained here .

In the caption, the user has written about her entire family needing to isolate and be tested after her initial positive result. But it was after the rest of the family tested negative, she said, that she wondered if her own result had been false. She wrote: “They were all negative strange really for a very highly deadly (MAN MADE) [virus]. And so I wondered if this was a false result I’m aware not everyone gets antibodies my main point is why didn’t any of my family test positive why did no one else from work test positive!!!”

Another user who screenshotted the original post to share it on his own account wrote: “So many apparently intelligent people who are still unable to see through the lies.”

Firstly, there is no proof to back the claim that SARS-CoV-2, the virus that causes COVID-19, is “man made”. Experts have repeatedly said they believe the virus was initially transmitted from animals to humans, and the World Health Organisation (WHO) has said “all available evidence” points towards it having a non-human, zoonotic source (here).

Testing positive for the new coronavirus also does not definitively mean your close contacts at home and work will subsequently contract the virus – although it may increase the risk (here, here, here) .

The antibody test, meanwhile, searches for evidence that antibodies have been developed in the body to fight the coronavirus, but a negative result also does not mean you have absolutely not had the virus (here). It simply means relevant antibodies have not been detected. According to an NHS leaflet discussing the antibody test, it is "not guaranteed to identify everyone who has had the virus," and therefore, “some people who have been infected may still have a negative test.” (here).

There are several factors that can explain this. Antibodies are often developed at any time between one and three weeks after infection (here, here), but can sometimes take between eight and ten weeks to be picked up (here), or may never be detected at all (here, here). They also weaken over time (here).

As well as this, antibodies are just one part of the body’s immune response to the virus (here). They come alongside T cells, which are white blood cells that act as “killer cells” against infection. Scientists are currently researching the role of T cells in fighting COVID-19, and whether they affect a level of antibody response (here, here).

Finally, no test is 100% accurate. The rate of false positive coronavirus tests in the UK is not known, as no studies into this have been carried out. However, previous testing for other viruses by the same means has shown evidence of some false positives (here) .

A recent study of antibody tests on people being treated in hospital found detectability varied depending on the time the test was taken. It also noted more research needed to be carried out on people outside of hospital settings – and therefore those with milder cases of the illness (here) .


Misleading. These screenshots do not present evidence that the new coronavirus is a lie. Testing positive for coronavirus does not immediately mean your close contacts will be infected. A negative antibody test does not confirm that you were never infected.

Read more about our work to fact-check social media posts here .