SARS-buster on negatives turning positive, new wave in China and dexamethasone
Patients can remain positive for a long period of time, sometimes longer than a month or even two. Often these patients test negative but then positive again. It is always low levels of the virus, said Prof.
Malik Peiris, Professor of Virology at the
School of Public Health, Hong Kong University, when asked by the Sunday
Times about the Sri Lankan who tested positive after discharge from hospital.
“Studies done by others and also us show that 14 days after illness-onset and once the patient has fully recovered from the symptoms, such low-level virus shedding is not highly infectious. In fact, Hong Kong changed its guidelines for the discharge of patients who have recovered from COVID from hospital a few months ago and we do not necessarily need to have negative PCR before patient discharge. I believe the WHO is also likely to make such a change,” he said.
With regard to a new wave hitting China, Prof. Peiris said the virus outbreak was caused by a European lineage virus, likely introduced via travel from Europe. But this did not mean that the virus was behaving differently in any way. Any lineage of virus can cause major outbreaks, similar to what happened in Wuhan in January/February.
When asked what a European lineage virus means, he said that there are signatures of mutations that can identify different geographic regions in a broad way to determine the ‘source’ of the virus. But this did not mean any change in the behaviour of the virus. There is one mutation in the spike protein of the virus which is now being recognised as possibly increasing virus fitness and perhaps transmission. Dexamethasone
The study on the benefits of dexamethasone shows how important well-designed clinical trials are, says Prof. Peiris, pointing out that dexamethasone and other corticosteroids have been used for a long time in patients with severe life-threatening pneumonia, but they have never been proven to be of benefit. There was some evidence, however, that uncontrolled use early in the disease can do harm.
“What this study shows is that dexamethasone is beneficial in patients who are severely ill – those in need of oxygen or are in the ICU, not in mild patients. We did use corticosteroids (a similar drug) during SARS in 2003 and it made a difference in some patients. But then, clinicians started using it earlier and earlier in the illness and this led to possible harm,” he says.
Prof. Peiris explains that dexamethasone and other corticosteroids suppress the immune system. So what is being done is to dampen down the "cytokine storm" that some patients develop which can lead to severe lung damage and death. But if you use it too early, the normal control immune mechanisms may also be impaired. So, it has to be used carefully.
The study on dexamethasone is being conducted in the United Kingdom by the University of Oxford and many hospitals. Corticosteroids usually provide relief for inflamed areas of the body especially in the case of severe allergies, skin problems, asthma or arthritis.