A Chinese herb - Spatholobus Suberectus Dunn - is a potential product in combating Covid.
A spray developed from its extract called SSP can act as an "invisible mask" covering the mouth and nasopharynx.
Researchers at Hong Kong University Chinese Medicine school said it has demonstrated broad antiviral activities against Covid
, H5N1 flu and AIDS.
Chen Jianping, the research team leader, said SSP can block the binding of the virus to the receptors, which can significantly reduce Omicron BA2 and Omicron BA4/5 infections.
Data showed the virus remains inhibited for 48 hours, but the duration of the effect in humans is yet to be studied.
The research team said SSD is a common Chinese medicine that is widely used in Guangxi and Yunnan and has been produced at low costs with high efficiency.
Chen said the spray can be used daily, three to five sprays each time, "just like wearing an invisible mask, and the cost is similar to that of a mask."
Chen added: "After a rodent model investigation comparing low and high dose administrations of SSP, no toxicity was caused, thus it is considered safe for people from all ages, and it also not antagonistic when used with Western medicine."
Liu Li, a research assistant professor of the AIDS Institute and Department of Microbiology, School of Clinical Medicine, HKUMed, said: "Since different GMP-batches show consistent antiviral activities, we are confident of the clinical development of SSP."