Sampling returns weak test

A weak-positive Covid-19 test was detected on Friday in routine wastewater sampling in South Auckland’s Papatoetoe last week, the Ministry of Health has revealed.

However, it said four samples – three from a site linked to Papatoetoe and one from a wider wastewater collection point that includes the suburb – returned negative results for coronavirus detection on Monday night.

The weak-positive result detected on Friday does not pose a risk to the community, the ministry said. ‘‘The most likely explanation for the weakpositive detection is continued shedding of the virus from the recovered Covid-19 cases from the February cluster who have returned home from the Auckland quarantine facility.’’

The ministry said people who recently had the virus may continue to shed fragments of it for some weeks after they have recovered, without being infectious.

‘‘Wastewater sampling can detect these fragments, which are not infectious and their presence is not considered a risk to the community,’’ it said.

‘‘This is supported by results from geospatial mapping linking the homes/ residential addresses of the individuals to the catchment area where the sample was taken. The new negative wastewater testing results also provide good evidence to support this. The recovered cases are no longer infectious and there is no evidence that the wastewater is infectious.’’

The Institute of Environmental Science and Research has been testing wastewater as part of an ongoing trial looking to detect outbreaks early.

Yesterday, the ministry also announced two new cases of Covid-19 in managed isolation and no new cases in the community. One of the cases had travelled from India and the other from the United States. Both were in managed isolation in Auckland.