A study of nine corona patients with a weakened immune system yields striking results; for example, researchers not only established the longest-lasting corona infection ever, but also encountered one of the first occult corona infections.

British scientists were eager to find out how SARS-CoV-2 (the virus that causes COVID-19) changes when it lingers in the body of people with weakened immune systems for a long time. “During the pandemic, new variants of SARS-CoV-2 have emerged,” explains researcher Luke Blagdon Snell. “Some of these variants are more contagious, more pathogenic or make vaccines less effective. One theory is that these viral variants evolve in people with immune systems that have been weakened — for example, from illness or medical treatments such as chemotherapy — and who can become infected by the virus for a long time.” To explore that theory further, scientists studied people with weakened immune system and a long-term corona infection. “We wanted to investigate which virus mutations occur in these people and whether new variants also arise.”

The research

The researchers collected nine people with a weakened immune system. In their case, their weakened immune system could be traced back to the fact that they had previously had an organ transplant, suffered from HIV or cancer, or received treatments in the fight against other diseases that affected their immune system. All participating test subjects tested positive for corona for at least eight weeks in a row. And although some could be declared corona-free a few weeks later, there were also two people whose infection lasted considerably longer – more than a year (!).

505 days

One of the subjects tested positive for corona 505 days before his death, but continued to test positive continuously throughout the period between that first positive test and the day of his death. It means that his infection lasted for 505 days – or just over 16 months. And that’s a record; never before have researchers seen such a long-lasting corona infection.

Whether that record will hold for long is doubtful. One of the other test subjects has already tested positive for 412 days and could therefore break that record.

Occult infection

In addition to long-term infections, while monitoring these corona patients, the researchers also encountered one of the first so-called ‘occult corona infections’. Occult infections describe a situation where – for example, thanks to a negative test – it is assumed that someone has completely cleared the virus, but later it turns out that there is still an infection, the researchers say. We have seen this before with other viruses, such as the viruses that cause Ebola or hepatitis B, and it differs from Lung COVID, where the virus is usually out of the body, but the symptoms still persist.”

The patient with the occult corona infection that the researchers describe in their study developed corona symptoms and tested positive for some time. But after a few months – and several negative tests – the patient developed corona symptoms again. A PCR test came back positive and an analysis of the virus he was carrying revealed that it was the Alpha variant. However, that variant was no longer available in Great Britain at that time. “It suggests that the virus has been present in the body since the initial infection, but went undetected for some time.”

Mutations and new variants

The research also seems to provide a little more insight into the origin of mutations and new virus variants. For example, the coronavirus was found to develop at least one mutation in five of the nine patients that we also see in the so-called ‘concerning variants’. “It provides us with evidence that mutations we find in variants of concern arise in patients with weakened immune systems and supports the idea that new variants of the virus can develop in individuals with weakened immune systems,” the researchers said. “However, it is important to note that none of the individuals in our study developed new variants that grew into widespread variants of concern. Moreover, while this study shows that new variants can arise in individuals with weakened immune systems, it remains unclear whether previous variants of concern (such as Alpha, Delta and Omikron) arose in the same way.”

Four of the nine patients with a long-term corona infection eventually died. Of the five remaining patients, two were treated with antibodies and antivirals, after which they lost the virus. Two other patients did not undergo treatment. And a third patient – ​​despite treatment – ​​still tests positive. “Patients with weakened immune systems and persistent infection often fare badly,” said study researcher Gaia Nebbia. “New treatment strategies are urgently needed to deal with their infection. And in this way the emergence of variants can also be prevented.”