Sydney, Sep 19 (IANS): Studying bats' responses to SARS-CoV-2 may provide key insights into how and when to best use existing therapies for Covid-19, and to develop new treatments, suggests a review.

The review, published in the journal Science Immunology, explores how the virus that has caused the current pandemic wreaks havoc on the human immune system.

The review, led by Monash University, showed that the common ancestor to the current Covid virus likely appeared in bats between 40 and 70 years ago, "though the exact bat species or intermediate host involved in the 2019 outbreak remains elusive."

Bats contract the virus but show minimal disease.

While bats can infect each other with SARS-CoV-2 they show no clinical effects nor show the same issues in the lungs that impact humans so badly.

The teamed suggested that some of the ways bats appear to resist Covid could be used in therapeutics such as fine-tuning the human immune response to the virus in ways that bats seem to use, including boosting type I and III interferon responses or -- once severe illness has developed -- blocking inflammasomes to mimic what happens in bats.

"Preventing progression to severe disease, or effectively treating it -- in other words emulating bats -- would markedly relieve suffering and save lives," said Professor Marcel Nold from Monash University.

Since first identified in December 2019, SARS-CoV-2 has mutated, and the variant strains Alpha, Beta and Delta are more infectious than the original strain.

Specifically, the Delta strain is 60-79 per cent more transmissible again than the Alpha mutant, and presumably more deadly, according to Nold.

He added there remains an urgent "need for effective therapies, at least in part because of the emergence of mutations."

The team warned that "preventing SARS-CoV-2 infection, or enabling patients to eradicate it, represents the ultimate goal in combating Covid-19: but it is uncertain when either will become reliably possible."

"Therefore, efforts at identifying safe and effective therapies to prevent Covid from progressing to the moderate and severe disease stages, are critical in the fight against the disease," Nold said.

Nold noted this "could minimise the excessive inflammation, immune exhaustion and the cytokine storms that are experienced in humans."