Coronavirus Covid-19: How ‘super spread’ fueled the NZ outbreak

Researchers have reconstructed New Zealand’s main Covid-19 outbreak to find that one in five adults was responsible for up to 85 percent of the spread of the virus.

The new analysis, published in PLOS One magazine, has highlighted the importance of targeting super spreader events to combat outbreaks.

It was also suggested that children under the age of 10 infected fewer people on average and were less likely to be “super-spreaders,” which were defined as infecting more than five other people.

New Zealand recorded nearly 1,500 Covid-19 cases between February 26 and May 22 of last year, before a nationwide shutdown and several other major measures effectively eliminated the virus.

In the study, Associate Professor Alex James and her fellow Te Punaha Matatini modelers used a wealth of case data, much of it collected through contact tracing, to uncover patterns in how the virus spread in those crucial months. .

They found that, before the move to alert level 4, more than half of all domestic cases resulted in at least one secondary case.

But age influenced the number of people to whom an infected person could transmit the virus.

The model showed that the effective reproduction number (R), the average number of secondary cases, was expected to be around 0.87 for children under the age of 10, 1.49 for people between 10 and 65 and 1 , 51 for those over 65.

“Although children under the age of 10 were equally likely to infect at least one person, adults tended to infect more people than children under 10,” the researchers reported.

Cases among adults and seniors also had a “significant” probability (6 percent in the 10-65 group and 7 percent in the 65+ group) of being a super spreader.

During the lockdown, the R number fell below one for all these age groups, except those over 65, something that may be due to the fact that care centers for the elderly are overrepresented in the data from the later stages of the epidemic.

Overall, the researchers pointed to 29 super-spreaders, of which 21 had Covid-19 symptoms before the lockdown began.

Of the remaining eight who presented symptoms during the confinement, six participated in care groups for the elderly.

The study also highlighted that children under the age of 10 tended to have a lower “secondary attack rate,” a measure that defines the likelihood of an infection spreading among a group of close or susceptible people, such as a household.

That was in line with studies abroad, as was the finding that “overcast” events contributed significantly to transmission.

“Our results show that among adults, 20 percent of cases are responsible for 65 to 85 percent of transmission,” the researchers said.

“This suggests that interventions targeting overcasts or overcast events may be particularly effective in reducing the spread of Covid-19.

“These can include restrictions on the size of the meeting, particularly in closed environments or crowded spaces.”

Meanwhile, another article just published in the US journal Emerging Infectious Diseases has highlighted the crucial role that real-time genomic sequencing played in the country’s next major outbreak.

As health officials struggled to contain the August Auckland cluster, which ultimately led to 179 infections and three deaths, scientists helped link the cases by sequencing the genomes of the positive samples.

In all, they were able to generate genomes from about 81 percent of the laboratory-confirmed samples, or 145 of the 179 cases, and then compared them to the available global genomic data.

That quickly told them that the virus behind the outbreak was part of a single group and therefore had emerged from a single introduction into the community.

“In fact, the timing and duration of the blocking measures were reported in part on the basis of these data,” said the authors of the study, led by Dr. Jemma Geoghegan, a virologist at the University of Otago and ESR, and Dr. Jordan Douglas, a researcher at the University of Auckland.

“Overall, real-time viral genomics has played a critical role in eliminating Covid-19 from New Zealand and has since helped prevent additional regional lockdowns, resulting in significant financial savings.”

Still, they said the important tool had been limited by the “skewed nature” of global sampling, including the contribution of very few genome sequences from certain regions.

“Therefore, we advocate that potential sampling biases and gaps in available genomic data be carefully considered when trying to determine the geographic origins of a specific SARS-CoV-2 outbreak,” they said.

“Analyzes should consider all available evidence, including from genomic and epidemiological sources.”