Meningococcal Disease - Background Information

Meningococcal Disease
Background Information

Main findings from this study
 Household crowding is the most important risk factor for meningococcal disease in Auckland children <8 years of age. Children who live with lots of adolescents and adults in small houses have a greater chance of developing this disease than other children develop.
 The most important aspect of crowding is the number of household members 10 years of age or over living in the house.
 The effects of crowding apply equally to Europeans, Maori and Pacific Island children (the small number of children in other ethnic groups were included with Europeans).
 The meningococcal disease epidemic is affecting all of New Zealand and overcrowding is also likely to be an important risk factor throughout the country.
 Although the study has identified an important risk factor for this disease, this risk factor does not explain all cases. Cases also occur in families that do not live in overcrowded conditions.

Meningococcal disease
 Meningococcal disease is a bacterial infection, with two main forms: meningitis, which is an infection of membranes over the brain and septicaemia, which is an infection of the blood stream
 The disease has a fatality rate of 4-5%, or 1 in 20 cases.
 Some of those who survive the disease suffer serious long-term effects, including loss of limbs, serious scarring, hearing loss and neurological damage.
 Meningococcal disease is different to amoebic meningitis, which is very rare and caught from hot pools and viral meningitis, which is quite common and much less serious.

How people catch meningococcal disease
 The bacteria (germ) occurs naturally in the throats of many of us (>10% of adolescents and adults)
 The bacteria is passed from these carriers by coughing and by saliva contact (kissing and sharing food or drinks)
 Most people who are carriers will not know they have the germ in their throats.
 It is very rare for the bacteria to cross into the blood stream and cause disease. It is not known exactly how or why this happens. However, exposure to other respiratory infections and tobacco smoke may increase the risk of this happening.

Long term trends in the New Zealand epidemic
 NZ is now in the 10th year of the meningococcal disease epidemic, which began in mid-1991.
 There has been a steady increase in cases from mid-1991 to 1997.
 Since 1997 the epidemic has reached a plateau with 400-600 cases a year which is a rate about 10 times higher than pre-epidemic level of about 50 cases a year; 1997 – 604 cases; 1998 – 404 cases; 1999 – 505 cases
 2000 (first 6 months) – 202 cases (implies a total for the year of 500-600 cases if the current trend continues)
 The epidemic has now caused over 3300 cases and 150 deaths.
 New Zealand’s rates are by far the highest in the developed world.

People who are most at risk of getting meningococcal disease
The main features of the epidemic have stayed fairly constant:
 Highest rates of disease are in those under 1 year. Overall about half of the cases are under 5 years.
 There are much higher rates in Maori (2.5 x rates in Europeans) and Pacific Island People (4x rate in Europeans).
 It is important to remember that this is not just a disease affecting Maori and Pacific Islands people. More cases occur in Europeans (207 cases out of 505 in 1999) than in Maori (184 cases in 1999) and Pacific Islands people (100 cases in 1999).
 Highest rates are in the Northern half of the North Island: South Auckland, Central Auckland, Northland, Rotorua, Bay of Plenty
 Typically, 75% of cases occur over the winter and spring period. Peak months are usually July, August, and September.
 During the epidemic, overall rates of disease have risen in all age groups, ethnic groups, geographic areas and seasons of the year. It is therefore a problem that the entire New Zealand population needs to be concerned about.
Reasons for the epidemic
 Meningococcal disease epidemics are uncommon in developed countries, but have occurred (e.g. Norway 1970’s, US Northwest in 1990’s). They may last for 10 or more years.
 The NZ epidemic is more intense than those seen in other developed countries are.
 Changes in the meningococcal disease organism are also likely to be contributing to the epidemic. The increase in cases coincided with the appearance of a new strain of the organism (B:4:P1.4). This epidemic strain now causes over 80% of cases.
 Rates are highest for people living in deprived areas, after controlling for age and ethnicity. This suggests that environmental factors such as crowding are contributing to the elevated rates of disease seen in some populations.

The importance of early recognition and treatment
 In its early stages meningococcal disease may look like other common winter infections – the person will be unwell, with a high temperature, not eating and sometimes vomiting.
 Key features with meningococcal disease are:
 The person gets worse quickly
 They may show signs of bleeding under skin - bright red spots and large bruises. This is a particularly serious feature.
 The sick person needs to be seen by a doctor immediately. Take the person straight to hospital if you are worried.
 The disease responds well to antibiotic treatment and the earlier the better. Most people (over 80%) make a complete recovery
 People given antibiotics before they get to hospital do much better. The fatality rate among those seen by doctor and given antibiotics before hospital admission was 1.7% (10 / 579) over the 1995-99 period compared with 3.8% (33/863) in those who saw a doctor but didn’t get such treatment.

ENDS

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