Guangdong’s coronavirus success shows an outbreak can be controlled, study finds
- More than 1.6 million Covid-19 tests have been carried out in the southern Chinese province
- Oxford researcher says studying virus genomes can help reveal transmission patterns as well as travel and contact history
Researchers from the University of Oxford and the Guangdong Centre for Disease Control and Prevention (CDC) analysed the genomic sequences of 53 patients from Guangdong. Their study revealed that the outbreak in Guangdong was mostly made up of independent cases introduced from outside the southern province instead of local transmission, which was around a quarter of the total cases in the province.
The researchers credit the containment of community spread in Guangdong to mass testing, tracing and isolation.
“Our work in Guangdong province shows that high levels of very early testing, together with active case tracing and strict isolation, can bring an outbreak under control,” said Dr Lu Jing from the Guangdong CDC and co-author of the study.
By March 19, Guangdong had 1,388 confirmed Covid-19 cases, the highest outside Hubei. Locally transmitted cases were estimated to be 336, and two-thirds – or 1,014 – had a likely exposure history in Hubei. Around 1.6 million tests were performed, the paper said.
As of Thursday, this testing rate of 14,159 tests per million people surpassed that of South Korea, which has one of the highest testing capacities in the world with 11,400 tests per million. China has not revealed the testing rate for the country as a whole.
“We find that Sars-CoV-2 lineages were imported multiple times into Guangdong during the second half of January 2020,” the researchers said, using the clinical name for the coronavirus.
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Combined with information on travel history or exposure to other infected people, the gene sequencing used in the study can help reveal the transmission of cases more clearly.
“For example, the largest Guangdong phylogenetic cluster comprises eight sequences, none of which are placed at the root of the cluster, and it is tempting to conclude that the entire cluster derived from community transmission within Guangdong,” the scientists wrote.
“However, six of the eight genomes reported travel from Hubei and therefore the cluster in fact represents multiple Sars-CoV-2 introductions into Guangdong, with dates of symptom onset around or shortly after the shutdown of travel from Wuhan.”
Study co-author Professor Oliver Pybus, of the University of Oxford, said it was important to analyse the virus genomes in combination with other information to better assess the evolution and transmission of the coronavirus.
“We know already that changes to the Covid-19 genome accumulate more slowly than for other viruses such as influenza,” he said.
“This means the Covid-19 virus is moving and transmitting faster than it mutates. So it’s crucial to analyse the virus genomes in combination with detailed epidemiological information.”
