Scientists have found a new version of the swine flu in China which also has the potential to trigger a pandemic.
The disease, which has emerged recently, is carried by pigs, but can infect humans.
Scientists are worried that there will be a repeat performance of Covid-19, where the virus will mutate further in a short time and spread quickly until it results in a pandemic.
As it is still a new disease, people have little if any immunity to the virus and so scientists are following it closely.
Scientists write in the Proceedings of the National Academy of Sciences that they have advised that measures to control the virus in pigs and the meat-producing industry, in order to prevent the spread of this new disease, should be swiftly implemented.
The virus, called G4 EA H1N1, can spread to human cells, particularly the lungs.