More than 100 people in Auckland, Waikato and the Lake Taupo area have been assessed for measles risk related to the outbreak of the disease among those who attended a hip-hop event in Sydney.
Some have been asked to stay in voluntary isolation at home because they are not immune to measles and are at risk of having caught it from one of the confirmed cases. Some are in isolation awaiting results of testing of their blood for immunity.
Measles is one of the most highly communicable of all infectious diseases. More than 90 per cent of non-immune people who have contact with a measles case will catch the illness. Nearly a third of cases develop complications. The fatality rate in Western countries is around one in 1,000 cases, and much higher in the Third World.
An 11th New Zealand case was confirmed yesterday - in the Turangi/Taupo area. Ten of the cases are in that area and from two extended families; one is an 18-year-old woman from Auckland. The cases range in age from 5 to 28.
Four of the New Zealand cases attended the "World Supremacy Battlegrounds" hip-hop street dance competition, held in Sydney on December 7 and 8. The rest are from their extended families.
The first notified case following the competition - an Adelaide competitor - came to light last Friday and a Sydney case also linked to the event was notified this week, the NSW Government health service said.
Public health nurses and doctors have followed up around 40 contacts of the Auckland case and more than 50 contacts of the Turangi/Taupo cases. Most of these people are immune to measles because they have been fully vaccinated or were born before 1969 and are therefore expected to have natural immunity from childhood exposure to measles.
Officials have been unable to trace several people because they are away from home and cannot be reached by phone.
Waikato public health unit spokeswoman Mary Anne Gill said an official had contacted around 20 people in Hamilton and Huntly who attended the Sydney competition.
Auckland public health specialist Dr Simon Baker said nurses had traced 90 per cent of the Auckland case's contacts, of whom 90 per cent were immune to measles.
Bay of Plenty/Lakes public health specialist Dr Neil de Wet said nine people in his area had been asked to stay in quarantine until it was clear they were not infected.
"If you live in the Turangi/Taupo area or if you're planning to visit there, it's good to be aware that we do have a measles outbreak. If you're under 45 and not immunised we advise you to get immunised."
The measles-mumps-rubella vaccine is state-funded for children, and for adults known to be susceptible to any of the three diseases.