Waikato Regional Council is urging residents to report any sightings of wild rabbit carcasses in areas where the RHDV1 K5 virus was released in April.
Landowners are being urged to continue with their rabbit control operations over winter.
The virus was released in Taupo, Kinloch, Omori/Kuratau and Whakarawa, as well as Matarangi, Pauanui, Whangamata, Thames, Hamilton and Cambridge/Karapiro.
"To be able to assess the effectiveness of the K5 release we are keen to hear of any sightings of wild rabbit carcasses so they can be collected for testing," said council biosecurity pest animals team leader, Brett Bailey.
"To date we have had only a couple of reports — one in Karapiro and another in Taupo — and there could be a number of reasons for this.
Rabbit densities dropped significantly throughout the region, particularly in Kinloch, prior to the K5 release. We think this could be due in part to a spike in the pre-existing virus.