Paolo Rossi Castelli 9 June 2022 18 min read

Are ‘viral ghosts’ the cause of Long Covid?

Two new studies confirm that fragments of the SARS-CoV-2 virus remain in the intestines of a significant percentage of people affected by the long version of the disease, causing a range of side effects.


They are called ‘viral ghosts’ and they could make an important contribution to research into the causes of the long-term consequences of the SARS-CoV-2 coronavirus infection, i.e. the syndrome officially called PASC (from Post Acute Sequelae of Covid 19), but better known as Long Covid.

They are the virus' cellular debris, sometimes fragments of nucleic acids (RNA) or whole proteins, still present in the body. Although they are present in very small quantities (to the point of not being detectable with a molecular swab), they can probably trigger an immune or autoimmune response and thus cause one or more of over 200 symptoms associated with Long Covid.

Two new studies on Long Covid
The idea is not entirely new, but it had little support until now. However, two studies released just a few days apart, support it, as both show that viral ghosts are hiding in the intestines of at least some people infected with SARS-CoV-2 (and many of them affected by Long Covid).

In the first, published in the scientific journal Med, geneticists from Stanford University, California monitored the faeces of 113 people who had had mild to moderate Covid for ten months, and found that after nearly a year, just under 4% of them still had intestinal ghosts (less than the 49% in the first week and 12% after four weeks) and that this 'persistence' was associated with gastrointestinal symptoms. In the same period of study, respiratory tests were negative.

As part of the second study, carried out by researchers at the University of Innsbruck, Austria, and published (although still awaiting the final go-ahead) in the scientific journal Gastroenterology, 46 people with inflammatory bowel disease underwent various types of examinations over a period of up to 219 days after the first positive swab. Again, 32 of them were found to have viral ghosts and whole coronavirus proteins were present in 24 people, hidden inside CD8+ lymphocytes (important immune system cells).

However, it was not possible to obtain a new virus culture from the material taken from the ghosts, confirming that these are not complete viral particles, but merely fragments. But they can cause serious damage, as demonstrated by the fact that three quarters of those with ghosts had gastrointestinal symptoms, while those with no viral ghosts had none of these symptoms.

Long Covid: data becomes more compelling
As the scientific journal Nature also points out in an article on these studies, the latest data confirm others published in recent months, and the body of evidence is starting to become convincing. Autopsy investigations have also confirmed that SARS-CoV-2 lurks in virtually every organ, perhaps even carried by immune system cells like macrophages.

More information about hepatitis C, too
Extensive and complex research will still be needed to better understand why the virus lurks within these ‘reservoirs’ in some patients but not others, whether there are other reservoirs, what this presence causes, and whether any treatment aimed at eliminating ghosts can cure Long Covid. In any case, this syndrome, which according to a recent estimate affects around one hundred million people worldwide, is slowly becoming less obscure.

When all the steps are understood, it will also be possible to better investigate other post-viral syndromes that have a lot of features in common with Long Covid, like those that occur after mononucleosis or hepatitis C.

Read our article 'In the wake of COVID, a Hepatitis C vaccine is on the horizon'


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Paolo Rossi Castelli

Journalist since 1983, Paolo has been dealing with scientific divulgation for years, especially in the fields of medicine and biology. He is the creator of Sportello Cancro, the site created by on oncology in collaboration with the Umberto Veronesi Foundation. He collaborated with the pages of the Science of Corriere della Sera for several years. He is the founder and director of PRC-Comunicare la scienza.