Zika and Polio alerted as 'Public Health Emergencies of International Concern', 2016-17
During 2016-17, there were two serious diseases alerted as a ‘Public Health Emergency of International Concern’ by the World Health Organization :
- Polio (2014-present), and
- Zika (February-November 2016).
No cases of Polio were detected in New Zealand. In 2016 there were 99 cases of Zika imported, mainly from the Pacific. There was one locally acquired sexually transmitted case .
Mosquito-borne disease cases have increased in New Zealand since 2001
Five mosquito-borne diseases were detected in New Zealand in 2016 [2,3]:
- Four mosquito-borne viruses: Chikungunya, Dengue Fever, Ross River Virus and Zika
- One mosquito-borne parasitic disease: Malaria
The total number of yearly cases of mosquito-borne diseases is shown in Figure 1. In 2016, New Zealand recorded its highest total for all reported cases of mosquito-borne diseases since 2001. The upward trend was driven by an increase in the number of Dengue cases, and the emergence of Zika and Chikungunya since 2014.
Figure 1: Number of case notifications of mosquito-borne diseases in New Zealand, 2001-2016
Differences in the characteristics of people who had priority border health diseases
In 2015-16, among people diagnosed with mosquito-borne diseases in New Zealand, there were :
1. Differences in overseas travel
Almost all people diagnosed with mosquito-borne diseases in New Zealand, in 2015 and 2016, were thought to have acquired these diseases while travelling overseas. The exception to this was one locally acquired case of Zika in 2016, although this was most likely sexually transmitted.
The Asia-Pacific region was the major source of overseas infection.
2. Differences in gender:
Males were more than twice as likely to be diagnosed with Malaria (a mosquito-borne parasitic disease) as females in New Zealand, 2015-16. There were no differences in gender between people diagnosed with mosquito-borne viruses.
3. Differences in age:
Over the five year period 2012-16, children (<15) and older adults (65+) were less likely to be diagnosed with malaria compared to youth (15-24) and young adults (25-44).
Over the same period, those aged 15-64 were six times more likely to be diagnosed with mosquito-borne disease than children (<14) and three times more likely to be diagnosed with mosquito-borne disease than older adults (aged 65+)(Figure 2).
Figure 2: Incident rate of malaria and mosquito-borne viral diseases 2012-16, by age
Data Source: ESR, 2018. Data for years 2012-16 have been aggregated to produce crude age-specific rates age groups due to small counts.
4. Differences in ethnicity:
In 2016 Pacific and European/Other ethnicities had statistically significant increases in rates of mosquito-borne disease compared to 2015. The rate of mosquito-borne disease in Pacific people was nine times that of European/Other ethnicities.
In 2015, Asian people had a statistically significantly greater rate of malaria than European/Other ethnicities. However, in 2016 these rates were not significantly different
5. Socio-economic differences in rates of mosquito-borne disease:
From 2015 to 2016, there were statistically significant differences in the rates of mosquito-borne disease diagnoses in New Zealand by different levels of socio-economic deprivation (Atkinson et al 2014). More deprived areas had higher rates of mosquito-borne disease than less deprived areas.
Incidence rates were 8.7 cases of mosquito-borne virus diagnosis per 100,000 people living in the most deprived areas (NZDep2013 quintile 5) and 5.8 cases per 100,000 in the least deprived areas (quintile 1).
For Zika the difference in rates between deciles was even more pronounced. Incidence rates were 0.7 and 2.4 cases of Zika per 100,000 people living in quintiles 1 and 5, respectively [3,4].
6. Differences by region:
During 2015 and 2016, people living in the Auckland DHB tended to be more likely to be diagnosed with a mosquito-borne virus than people living in other areas. 126 of 573 cases (22%) were in Auckland DHB.
In 2015 and 2016, the Auckland DHB had the highest number of Zika cases diagnosed (32), followed by Counties Manukau (20), Waitemata (15), and Capital and Coast (9). Rates were significantly higher in Auckland when compared to Waitemata, Waikato and Canterbury. All other DHBs had low or zero case numbers.
See the factsheet 'Border health in New Zealand' for more detail.
1. World Health Organization. Global Alert Response (GAR). [Accessed March 2018]. Available from: http://www.who.int/csr/resources/publications/en/
2. Institute of Environmental Science and Research Limited (ESR). 2016. Notifiable Diseases in New Zealand: Annual Report 2016. Porirua: Institute of Environmental Science and Research Limited.
3. Institute of Environmental Science and Research Limited (ESR). Notifiable diseases EpiSurv data extraction. Porirua: Institute of Environmental Science and Research Limited. [2018 personal communication with ESR Senior Analysts]
4. Atkinson J, Salmond C and Crampton P. 2014. NZDep2013 Index of Deprivation. Wellington: University of Otago