Virologists are warning that the emergence of "Disease X", which could cause a future pandemic, might be associated with climate change.
Professor Emeritus Datuk Dr Lam Sai Kit said there was a high likelihood of Disease X occurring due to deforestation and the wildlife trade.
"Wildlife, especially bats, carry a lot of viruses. Migratory birds and pangolins carry the avian influenza virus.
"If we accept the view that Disease X originates from wildlife, then we should strengthen our surveillance not only on the illness in humans but also in wildlife and domesticated farm animals," he said.
He emphasised the lesson learned from Covid-19 was the significance of implementing measures to prevent spillover events, as evidenced by claims that the virus originated due to animal to human transmission.
Echoing Dr Lam, Monash University molecular virologist Associate Professor Dr Vinod Balasubramaniam said climate change increased the risk of future pandemics.
He said it was crucial to address climate change to prevent future pandemics.
"Deforestation, urbanisation and expanding the meat industry requires extensive livestock farming. These bring animals closer to humans and lead to the risk of diseases spreading from animals to humans," he added.
Both experts predicted that Disease X would be another respiratory infection, with asymptomatic individuals as carrier.
Dr Lam said Disease X might originate from a highly mutable virus in animals, with a high possibility of transferance to humans.
"The World Health Organisation (WHO) has made a list of priority viruses with the potential to be the causative agent of Disease X, which may be deadlier than Covid-19.
"We cannot predict its level of destructiveness and infectiousness.
"Although the causative agent of Covid-19 is highly infectious and spreads efficiently, it is not as deadly as other viruses, including Ebola and Nipah.
"Can you imagine what would happen if the X pathogen is as infectious as influenza and as deadly as Nipah (which has a mortality rate of 40-70 per cent)?"
Correspondingly, Dr Vinod said he believed the next outbreak in line would be a respiratory infection, with a high rate of human-to-human spread.
Infected humans often generate aerosols when they cough, sneeze or speak loudly.
Dr Vinod said there was a possibility that Disease X would be zoonotic (an infectious disease that is transmitted between species from animals to humans), like the human immunodeficiency virus (HIV) or acquired immune deficiency syndrome (AIDS).
He said he viewed the influenza virus, especially the H5N1 subtype, as a Disease X candidate.
The emergence of a new coronavirus strain with the ability to mutate, resembling the flu, would be another possibility as current vaccines are not designed to eradicate the virus.
"Until we have the vaccine that eradicates the virus, it will continue to evolve.
"Recent mass mortality in mammals due to the H5 subtype (Highly Pathogenic Avian Influenza) virus shows that it can adapt to mammals and become transmissive," he said.