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Scale of current measles outbreak - Expert Q&A
Over the past week there have been three confirmed new measles cases, bringing the total for 2019 up to 67, according to monitoring by the Institute of Environmental Science and Research (ESR).
The weekly measles report shows 52
of the 67 confirmed cases were in unvaccinated people, with
seven occurring in people who were fully vaccinated.
Last week, Canterbury DHB announced it was extending its vaccination campaign to a wider group of people.
The SMC asked experts to explain how this outbreak compares to previous ones in recent times – please feel free to use these comments in your reporting.
Dr Helen Petousis-Harris, Senior Lecturer, Vaccinology, University of Auckland, comments:
How does this outbreak compare to previous outbreaks in the past 10-20 years in terms of scale and how fast it's spreading?
"The current measles outbreaks (Canterbury and Auckland) are not bigger than previous outbreaks in the last few years. As it stands at the moment, 2009, 2011, and 2014 were significantly bigger. However, if we go back to the ‘90s we had a whopper in 1991 with thousands of cases and seven deaths and then managed to stave off another in 1997 with a mass vaccination campaign.
"I do not think we will see another 1990s episode – we do not have enough susceptible people in our community. However, the current outbreaks indicate we still have some gaps to close and with the global resurgence of this disease, we can expect more measles cases getting off a plane and walking through our communities.
"Measles is a notifiable disease and has been for many years. This means that every single case must be notified.
"While it has been rough on general practices trying to meet the needs of people presenting for vaccination it is great to see so many people fronting up and getting up to date with their MMR vaccinations. Ultimately this is going to help stop future outbreaks."
No conflict of interest.
Dr Jill Sherwood, public health physician, ESR, comments:
How does this outbreak compare to previous outbreaks in the past 10-20 years in terms of scale and how fast it's spreading?
"So far this year there have been 67 confirmed cases – with almost two-thirds of the cases linked to the current outbreak in Canterbury.
"After the introduction of the measles vaccine in 1969, measles continued to occur every year until 1980, with a pattern of 'low years' (an average of approximately 100 hospitalisations per year) alternating with 'high' or 'epidemic' years (an average of 300 hospitalisations per year). This was because vaccination rates were not high enough to prevent outbreaks.
"Increased uptake of the measles vaccine, which is thought to have reached 70 per cent or more by 1980, resulted in this epidemic cycle becoming more accentuated, with fewer cases and longer periods between epidemics.
"Measles virtually disappeared between the epidemic years which began to occur less frequently – 1984/85, 1991 and 1997. There were 400 hospitalisations in the 1984/85 outbreak and a total of 943 hospitalisations in the 1991 and 1997 epidemics, with seven deaths in 1991. No deaths occurred in 1997.
"We are not able to say how fast the disease is spreading in the current outbreak."
What triggers the notifiable diseases reporting? Is it a certain number of cases?
"Measles is classified as one of the notifiable diseases because it can have serious complications, including death, in a significant proportion of people infected, and is easily transmitted. The Ministry of Health says the Medical Officer of Health should be notified of any case of suspected measles so that cases can be quickly isolated and contacts given advice to reduce further spread.
"Generally the term epidemic is used when an outbreak involves at least several regions within a country – depending on the disease it might only be used if a national outbreak occurs.
"Note the term 'pandemic' is used when an epidemic is spreading to at least several countries.
"Outbreak and epidemic are often used interchangeably.
"ESR is responsible for the surveillance of all communicable diseases. Disease surveillance is the continuous monitoring of the frequency and the distribution of disease, and death, due to infections that can be transmitted from human to human or from animals, food, water or the environment to humans, and the monitoring of risk factors for those infections."
In what situation should someone be quarantined to prevent the spread of measles?
"Measles patients are infectious five days before and five days after the rash appears, and should be in isolation until that period is over.
"The disease is a highly infectious airborne virus which affects both children and adults. If you think you have measles, it’s important to call before visiting your doctor to avoid spreading the virus in the waiting room.
"It’s also important if you’ve been in contact with someone with measles while they were infectious and you are not immune (not fully vaccinated or born before 1969) that you avoid public places, such as schools or early childhood centres, or community gatherings, until 14 days after your last exposure to the infectious case.
"By isolating or quarantining yourself you will help protect vulnerable people including babies, pregnant women, cancer patients and others who are unable to be immunised and for whom the impact of the disease can be devastating.
"People travelling overseas are advised to make sure they are fully immunised against measles before they go."
Are all the cases in the current outbreak in unvaccinated people?
"As expected, the majority of cases are in unvaccinated people. While some of the cases are in vaccinated people, most of them have received only one dose."
No conflict of interest.
ends
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