The virus that causes Covid-19 has not mutated into different types, according to new analysis.

Recent research had suggested more than one type of SARS-CoV-2, the virus that causes Covid-19, is now circulating, with one strain being more aggressive and causing more serious illness than the other.

However using analysis of SARS-CoV-2 virus samples, scientists from the Medical Research Council-University of Glasgow Centre for Virus Research (CVR) have found only one type of the virus.

Viruses, including the one causing Covid-19, naturally accumulate mutations – or changes – in their genetic sequence as they spread through populations.

It is important people are not concerned about virus mutations – these are normal and expected as a virus passes through a population

Scientists said most of these changes will have no effect on the biology of the virus or the aggressiveness of the disease they cause.

Dr Oscar MacLean, from the CVR, said: “By analysing the extensive genetic sequence variation present in the genomes of the SARS-CoV-2 virus, the evolutionary analysis shows why these claims that multiple types of the virus are currently circulating are unfounded.

“It is important people are not concerned about virus mutations – these are normal and expected as a virus passes through a population.

“However, these mutations can be useful as they allow us to track transmission history and understand the historic pattern of global spread.”

It was reported earlier this year that scientists had found two or three strains of SARS-CoV-2 circulating in the population, evidenced by certain mutations that had been detected.

However extensive analysis by the team found these detected mutations are unlikely to have any functional significance, and, importantly, do not represent different virus types.

The centre’s CoV-GLUE resource tracks SARS-CoV-2’s amino acid replacements, insertions and deletions, which have been observed in samples from the pandemic.

To date the database has catalogued 7,237 mutations in the pandemic.

Scientists said that while this may sound like a lot of change, it is a relatively low rate of evolution for a virus that has ribonucleic acid (RNA) as its genetic material.

They expect more mutations will continue to accumulate as the pandemic continues.

Most observed mutations would be expected to have no, or minimal, consequence to the virus’s biology, however tracking these changes can help scientists better understand the pandemic and how Covid-19 is spreading in the community.

The study is published in Virus Evolution and the work was funded by the Medical Research Council.

Elsewhere, other scientists say they have identified a new coronavirus strain that has become dominant worldwide.

The researchers have been tracking changes to the “spike” of the virus that gives it its distinctive shape.

They warn that in addition to making it grow faster, the mutation may make people vulnerable to a second infection after a first bout with the disease.

The Los Alamos team, assisted by scientists at Duke University and the University of Sheffield in England, identified 14 mutations.

They write: “The mutation Spike D614G is of urgent concern.

“It began spreading in Europe in early February, and when introduced to new regions it rapidly becomes the dominant form.”

The new strain has been the dominant strain across the world since mid-March, the scientists say.

The study from the Los Alamos National Laboratory in New Mexico, hasn’t yet been reviewed by other scientists and formally published.