Contents

12 Meningococcal disease

12.3 Epidemiology

12.3.1 General

Those particularly at risk of meningococcal disease are children aged under five years, although all age groups can be infected. There is a higher case fatality rate in adults. The presentation may be non-specific in young infants.

Close contacts of primary cases of meningococcal infection are at increased risk of developing infection, such as within families,1 early childhood education services, semi-closed communities, schools, correctional facilities and military recruit camps. Students living in hostel accommodation may also be at higher risk.2–4 In health care settings, only those with close exposure to oropharyngeal secretions of patients with meningococcal disease (as may occur during intubation or resuscitation) and microbiology laboratory workers are considered to be at increased risk.

It is not possible to calculate the incubation period for meningococcal disease for sporadic cases. Secondary cases (ie, in contacts of known cases of meningococcal disease) who develop the disease usually do so within four days, but it can be up to 10 days. The infectivity of patients with meningococcal disease is markedly reduced after 24 hours of antibiotic therapy, although treatment with rifampicin, ceftriaxone or ciprofloxacin is necessary to reliably eradicate nasopharyngeal carriage and hence relax infection prevention and control precautions (see section 12.8.1).

Serogroup A disease

Group A disease is rare in New Zealand (the last large outbreak was in 1985/86) but it can cause massive outbreaks of disease, such as the regular epidemics in the sub-Saharan Africa meningitis belt, where attack rates may approach 1000–2000 cases per 100,000 people per year. There have been outbreaks of meningococcal disease associated with the Hajj pilgrimage, and meningococcal vaccination is recommended before travel.5 Documented evidence of vaccination is required by the Saudi Arabian Ministry of Health for anyone going to the Hajj pilgrimage.

Serogroup B disease

Group B disease is often the most common serotype causing infection, and can cause epidemics that start slowly and persist for five or more years. A very large epidemic of group B meningococcal disease, caused by a single subtype (B:4:P1.7b,4), occurred in New Zealand between 1991 and 2007, with a peak incidence of 200 cases per 100,000 children aged under 12 months in 2001. The epidemic disproportionately affected Māori and Pacific people.

Serogroup C disease

Group C meningococci have been occasionally associated with small clusters of meningococcal disease cases in schools and universities, and in 2011 there was a more widespread outbreak in Northland.

Other serogroups

Sporadic cases, particularly in the elderly, are seen often in individuals presenting with non-specific febrile illnesses and pneumonia.

12.3.2 New Zealand epidemiologyTop

Incidence and mortality

In 2012 the rate was 1.9 cases per 100,000 population, with a total of 85 cases notified (74 confirmed)6 (Table 12.3).

Table 12.3: Notified cases and rates of meningococcal disease, 2008–2012

Year Number Rate/100,000 population
2008 122 2.9
2009 133 3.1
2010 97 2.2
2011 119 2.7
2012 85 1.9

Source: Lopez L, Sexton K. 2013. The Epidemiology of Meningococcal Disease in New Zealand in 2012. URL: https://surv.esr.cri.nz/PDF_surveillance/MeningococcalDisease/ 2012/2012AnnualRpt.pdf (accessed 10 September 2013), Table 1.

The annual number of notified cases of meningococcal disease in New Zealand since 1970 is shown in Figure 12.1. There were 68 notifications in 2013.

Figure 12.1: Notified cases of meningococcal disease, 1970–2013

Figure 12.1: Notified cases of meningococcal disease, 1970–2013

Source: Institute of Environmental Science and Research

Meningococcal infection rates remain consistently higher in Māori and Pacific people compared with the total population. Māori had the highest disease rate in 2012 (4.5 per 100,000), followed by Pacific people (3.7) and European or Other (1.4). The highest disease rate by age group was for Māori children aged under 12 months (49.0 per 100,000).6

In 2012 the highest age-specific disease rates were among those aged under 1 year (19.8 per 100,000 population, 12 cases) and 1–4 years (5.6 per 100,000 population, 14 cases), with a secondary peak in the notification rate for those aged 15–19 years (4.8 per 100,000 population, 15 cases).6 Figure 12.2 shows the age distribution of the 456 strain-typed cases from 2008 to 2012. Group B strains were the most prevalent in all age groups except for the age 15–19 years group, in which Group C strains were the most prevalent.

Figure 12.2: Age distribution among strain-typed meningococcal disease cases, 2008–2012 cumulative data

Figure 12.2: Age distribution among strain-typed meningococcal disease cases, 2008–2012 cumulative data

Source: Institute of Environmental Science and Research

Six fatalities occurred in 2012, a case fatality rate of 7.1 percent. Two fatalities were due to group B strains (one from the epidemic strain) and four were due to group C strains.6

Strain types

Group B strains were the most prevalent in 2012, causing over 60 percent of the confirmed cases. The group B strain (B:4:P1.7b,4) responsible for the epidemic caused 22.1 percent of all meningococcal disease in 2012. The number of cases of meningococcal disease caused by group C strains has increased since 2007 (Figure 12.3), particularly the group C:P1.5-1,10-8 strain.6

Figure 12.3: Groups and dominant subtypes among strain-typed meningococcal disease cases, 2008–2012

Figure 12.3: Groups and dominant subtypes among strain-typed meningococcal disease cases, 2008–2012

Source: Institute of Environmental Science and Research

Between 2008 and 2012, the number of cases due to strains targeted by the MeNZB vaccine (B:4:P1.7b,4) fell from 46 to 15. In contrast, the number of cases due to strains targeted by the group C conjugate vaccine significantly increased between 2008 and 2011 (from 12 to 32) and then decreased in 2012 to 23 cases. The trends in cases due to strains targeted by the quadrivalent vaccine (A, C, W135 and Y) are being driven by the increase in group C disease. Of the 25 cases in 2012 caused by strains targeted by the quadrivalent meningococcal vaccine, only two were caused by non-group C strains.6

Meningococcal conjugate group C vaccination is not on the New Zealand Schedule at present, but this recommendation could change if the incidence of group C meningococcal disease increases. In 2012 the group C rate was 0.51 per 100,000 population (23 cases). The UK had a total population rate of 2.10 per 100,000 when the group C meningococcal vaccination was introduced in 1999.7 In Australia the rate was 1.10 per 100,000 when the vaccine was introduced in 2003.