The sequencing of genomes in Covid-19 cases can help find where people contract the virus.
University of Otago microbiology and immunology senior lecturer Jemma Geoghegan said the genome sequence of he four recent Covid-19 cases were "pretty much identical, so we know that they have been transmitted from each other".
She said the Institute of Environmental Science and Research (ESR) would be sequencing all positive cases from now on "to tell us where they came from".
Geoghegan said the origin of the four new cases was unknown, "so we don't know the origin of the cluster that is forming. Genomic sequencing will hopefully tell us its likely origin".
ESR will now compare the details of these cases to the ones in managed isolation, as well as the rest of the world, and hopefully instruct a "family tree of viruses" and determine the chain of transmission.
Geoghegan said contact tracing remained vital. Genomic sequencing could help locate the origin of the Auckland cluster, while tracing helped piece together the chain.