Does Coronavirus Linger In The Body?

September 6, 2020

As millions of people are recovering from COVID-19, an unanswered question is the extent to which the virus can be “hidden” in people who appear to be recovering. If this is indeed the case, could this explain some of the lingering symptoms of COVID-19, or the risk of passing the infection on to others even after recovery?

I am a physician-scientist in infectious diseases at the University of Virginia, where I provide care for infected patients and conduct research on COVID-19. Here, I will briefly review what is currently known about chronic or persistent COVID-19.

What is a chronic or persistent viral infection?
Chronic or persistent infections can last for months or even years, during which time the virus is constantly being produced, albeit at low levels in many cases. These infections often occur in so-called immune privileged areas.

What is an immune privileged site?
There are several places in the body that are harder for the immune system to access and eradicate all viral infections. These places include the central nervous system, the testicles and the eyes. It has been suggested that the evolutionary advantage of having immune-privileged areas is that it protects areas like the brain from being destroyed by the inflammation that occurs when the immune system battles an infection.

Not only do immune privileged areas make it difficult for the immune system to access them, they also limit the proteins that increase inflammation. The reason for this is that while inflammation helps kill pathogens, it can also damage organs like the eyes, brain, or testicles. The result is an unstable truce where inflammation is restricted but the infection continues to fester.

Latent infection vs. ongoing viral infection
However, there is another way in which the virus can be hidden in the body and reappear later.

A latent virus infection is when the virus is present in the infected cells, but is dormant and does not reproduce. In a latent virus, the entire viral genome is present, and if the latency period ends and the infection becomes active, an infectious virus can be produced. The latent virus can integrate into the human genome – such as HIV – or exist in the nucleus as a self-replicating piece of DNA called an exon.

The latent virus can reactivate and give rise to an infectious virus, which can occur months to decades after the initial infection. Perhaps the best example is chickenpox, which, although seemingly wiped out by the immune system, can reactivate and cause shingles decades later. Fortunately, chickenpox and shingles can now be prevented by vaccination. An infection with a virus that can create a latent infection is a lifetime infection.

How does a virus become a latent infection?
Herpes virus is the most common viral infection that establishes a latent infection today.

It is a large family of viruses whose genetic material, or genome, is encoded by DNA (rather than RNA, as in the case of novel coronaviruses). Herpes viruses include not only herpes simplex viruses 1 and 2 – which cause oral and genital herpes – but also chickenpox. Other herpes viruses, such as Epstein Barr virus, which causes mononucleosis, and cytomegalovirus, which is a particular problem in immunodeficient people, can also emerge after the incubation period.

Retroviruses are another common family of viruses that can establish latency, but by a different mechanism than herpes viruses. Retroviruses such as HIV, which causes AIDS, can insert a copy of their genome into a part of the human genome, human DNA. There, the virus can remain in an infected person in a latent state indefinitely, because the viral genome is copied each time DNA replicates and cells divide.

It is difficult or impossible for the immune system to destroy a virus that has established a latent period in the human body. This is because there may be little or no production of viral proteins in the infected cells during the incubation period, making the infection invisible to the immune system. Fortunately, coronaviruses do not establish a latent infection.

Can a male sexual partner who has recovered from COVID-19 be infected with SARS-CoV-2?

In one small study, new coronavirus was detected in semen during active infection in a quarter of patients, compared to less than 10% of patients who apparently recovered. In this study, viral RNA was detected, and it is not yet known whether this RNA came from the still-infectious virus in the semen or from the dead virus; and if it was alive, whether it could be sexually transmitted. So many important questions remain unanswered.

The Ebola virus is very different from SARS-C0V-2, but it is an example of a virus that persists in immune-privileged sites. In some people, the Ebola virus survives in immune-privileged sites for months after the acute illness has healed. Ebola survivors have been documented to have persistent infections in the testes, eyes, placenta, and central nervous system.

The WHO recommends that male Ebola survivors have their semen tested for the virus every three months. They also recommend that couples abstain from sex for 12 months after recovery or until their semen tests negative for Ebola twice. As mentioned above, we need to know more about persistent neo-coronavirus infection before we consider similar recommendations.

Could the persistent symptoms after COVID-19 be due to the persistence of the virus?
Many people have delayed or incomplete recovery from COVID-19, and symptoms include coughing, shortness of breath, and fatigue. It seems unlikely that these constitutional symptoms are due to the persistence of the virus, as they do not come from a site of immune privilege.

Where does the new coronavirus persist after recovery from COVID-19?
Other sites where coronavirus has been detected include the placenta, intestines, blood, and of course, the respiratory tract. In women who are infected with COVID-19 during pregnancy, the placenta develops a vascular defect in the maternal supply to the placenta. However, the significance of this for fetal health is yet to be determined.

The new coronavirus can also infect the fetus through the placenta. Finally, the new coronavirus can also be present in the blood, nose, and palate for a month or more after infection.

There is growing evidence that SARS-CoV-2 can infect immune privileged sites and from there cause chronic persistent – but not latent – infections. It’s too early to know the extent to which these persistent infections affect the health of individuals such as pregnant women, or the extent to which they contribute to the spread of COVID-19.

As with many things in an epidemic, what is not known today will be known tomorrow, so stay tuned and remain cautious so that you do not get infected or, worse, spread it to others.