Five of the six major variants of the coronavirus circulating the globe appear to be more infectious than the original one which broke out in China, scientists say.
Chinese researchers sequenced the SARS-CoV-2 genome and released it to the World Health Organization and labs worldwide in January. Since then - as viruses do - it has evolved, with six major subtypes recorded as early as April.
"As with any virus, many mutations are ultimately benign, posing little to no risk to infected patients," the Michigan State University team said in a statement.
"Some mutations even reduce infectiousness. But some mutations lead to a more infectious virus."
The virus infects cells via a surface enzyme called ACE2. The scientists used a complex computer system called a neural network to simulate thousands of interactions between the SARS-CoV-2 virus and the human ACE2 receptor, finding five of the six subtypes had "increased binding affinity" - meaning they had an easier time getting in.
The sixth type had mutations that made it less infectious. Cluster III, as it's called in the study, was the predominant strain in Russia and South America. It also had a decent foothold in Europe and New Zealand.
The most common type here, Cluster II, is also dominant in China, India, Australia and southeast Asia, and was present in samples from every country sampled in the research. Its mutations gave it a "minor increase in infectivity" according to the computer modelling.
Cluster I, found mainly in Africa and the Middle East, showed the biggest increase in infectivity.
Guowei Wei, who developed the computer modelling, said the results were "consistent with available experimental findings". The research paper, which like much urgent research into COVID-19 has not yet been peer-reviewed, was published online.
The results also highlighted spots on the virus which had the potential to develop mutations that would help it become more infectious in future.
"It's extremely important to know whether future SARS-CoV-2 subtypes would pose an imminent danger to public health."
Viruses are able to mutate quickly because of their incredibly high rate of reproduction - it's the reason why each year we need a new flu vaccine, the previous year's shot no longer effective. Mutations are random - they're not deliberately engineered - but changes that increase a virus' chance of replication are more likely to be passed down to future generations.
