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Labs in China have produced covid-19 virus detection kits
ALEX PLAVEVSKI\/EPA-EFE\/Shutterstock<\/p><\/div>\n
Two strains of the new coronavirus are spreading around the world,\u00a0according to an analysis of 103 cases<\/a>. But the World Health Organization insists that \u201cthere is no evidence that the virus has been changing\u201d. So how many strains are there, and why does it matter?<\/p>\n Viruses are always mutating,\u00a0especially RNA viruses like this one, coronavirus SARS-CoV-2<\/a>. When a person is infected with the coronavirus, it replicates in their respiratory tract. Every time it does, around half a dozen genetic mutations occur, says Ian Jones at the University of Reading, UK.<\/p>\n When Xiaolu Tang at Peking University in Beijing and colleagues studied the viral genome taken from 103 cases, they found common mutations at two locations on the genome. The team identified two types of the virus based on differences in the genome at these two regions: 72 were considered to be the \u201cL-type\u201d and 29 were classed \u201cS-type\u201d.<\/p>\n A separate analysis by the team suggests that the L-type was derived from the older S-type. The first strain is likely to have emerged around the time\u00a0the virus jumped from animals to humans<\/a>. The second emerged soon after that, says the team. Both are involved in the current global outbreak. The fact that the L-type is more prevalent suggests that it is \u201cmore aggressive\u201d than the S-type, the team say.<\/p>\n \u201cThere do appear to be two different strains,\u201d says Ravinder Kanda at Oxford Brookes University in the UK. \u201c[The L-type] might be more aggressive in transmitting itself, but we have no idea yet how these underlying genetic changes will relate to disease severity,\u201d she says.<\/p>\n \u201cI think it\u2019s a fact that there are two strains,\u201d says Erik Volz at Imperial College London. \u201cIt\u2019s normal for viruses to undergo evolution when they are transmitted to a new host.\u201d<\/p>\n It is vital to know how many strains of the virus exist. Around the world,\u00a0multiple groups are working on a vaccine for the virus<\/a>. Any vaccine will need to target features that are found in both strains of the virus in order to be effective.<\/p>\n The differences between the two identified strains are tiny. In fact, they can\u2019t really be considered to be separate \u201cstrains\u201d, says Jones. And many of the genetic differences won\u2019t affect the production of proteins, and so won\u2019t change the way the virus works, or the symptoms it causes, he says. One is not more deadly than the other.<\/p>\n \u201cIn all practical terms, the virus is as it was when it originally emerged,\u201d says Jones. \u201cThere\u2019s no evidence it is getting any worse.\u201d The sentiment is echoed by the World Health Organization. The study by Tang and colleagues only suggests there is some genetic diversity of the virus \u2013 it doesn\u2019t mean it is changing, a representative told\u00a0New Scientist<\/em>.<\/p>\n But we can\u2019t say for sure. The study only represents 103 cases. A larger, online database has collated the sequencing results from 166 cases. Both represent a drop in the ocean of the almost 100,000 officially reported cases.<\/p>\n Jones says we can expect more strains to emerge. Epidemiologists generally agree that, once a person is infected with the coronavirus, they are unlikely to be infected again \u2013 unless the virus mutates to allow it to overcome the immune system\u2019s defences.<\/p>\n This \u201cselection pressure\u201d could lead to the outbreak of a new strain, says Jones. This is the case with seasonal flu \u2013 new variants crop up every year that can infect people whether or not they\u2019ve had flu in the past.<\/p>\n We could see the same pattern emerge for the new coronavirus in the coming years, says Jones. \u201cI don\u2019t see it going away any time soon.\u201d<\/p>\n Journal reference:\u00a0National Science Review<\/i>,\u00a0DOI: 10.1093\/nsr\/nwaa036<\/a><\/p>\nRead more:\u00a0Coronavirus: What are the worst symptoms and how deadly is covid-19?<\/a><\/h4>\n<\/div>\n