The way the Covid-19 virus functions suggests that it has a unique infectious profile, which may explain why it can be so difficult to treat, a major European review has revealed.

This unique profile may also explain why some people experience ‘long Covid’, the researchers said.

The review was produced by the European Group on Immunology of Sepsis (EGIS) -  a multidisciplinary group of scientists and doctors with a special interest in severe infection in patients admitted to ICU. One of its co-authors was Prof Ignacio Martin-Loeches, a consultant in intensive care medicine at St James’s Hospital and clinical professor in TCD’s School of Medicine.

“Despite international focus on the virus, we are only just beginning to understand its intricacies. Based on growing evidence we propose that Covid-19 should be perceived as a new entity with a previously unknown infectious profile. It has its own characteristics and distinct pathophysiology and we need to be aware of this when treating people,” he commented.

The researchers noted that there is growing evidence that the Covid virus infects both the upper and lower respiratory tracts. This is unlike “low pathogenic” human coronavirus sub-species, which typically settle in the upper respiratory tract and cause cold-like symptoms, or “high pathogenic” viruses, such as those that cause SARS and ARDS, which typically settle in the lower respiratory tract.

As well as this, more frequent multi-organ impacts, blood clots, and an unusual immune-inflammatory response not commonly associated with other, similar viruses, mean that Covid-19 displays a uniquely challenging set of characteristics.

The review also highlighted that while animal and experimental models imply that an overly aggressive immune-inflammation response is a key driver of the virus, things appear to work differently in humans. While inflammation is a factor, it is a unique dysregulation of the immune response that causes our bodies to mismanage the way we fight the virus.

This may explain why some people experience ‘long-COVID’ and suffer severe lung damage after infection, the researchers suggested.

“However, while the virus appears to have a unique infectious profile, “that doesn’t mean we should abandon existing best-practice treatments that are based on our knowledge of other human coronaviruses,” Prof Martin-Loeches said.

He added that what is needed is “an unbiased, gradual assembly of the key Covid-19 puzzle pieces for different patient cohorts – based on sex, age, ethnicity, pre-existing comorbidities – to modify the existing treatment guidelines”.

The review was published in The Lancet and can be read here.