Overcrowding and the risk of meningococcal disease

Media Release
Embargoed till midnight Thursday 10 August 2000

Overcrowding increases risk of meningococcal disease

Household crowding is the most important risk factor for meningococcal disease in Auckland children.

A three-year study provides evidence that the meningococcal disease epidemic has been driven, at least in part, by social conditions. It shows that while household crowding is unlikely to have caused the meningococcal disease epidemic in New Zealand, crowding has almost certainly intensified its effect among the most vulnerable, notably Maori and Pacific Island people living in Auckland. An important finding is that the effect of overcrowding applied equally to children of all ethnic groups.

The study showed that the risk of meningococcal disease was strongly associated with overcrowding in the child’s house. It found that it was the number of adolescent and adult household members that was important.

“Crowding increases contact between young children and adolescents or adults who carry the organism.” says ESR public health physician Dr Michael Baker, the principal investigator for the study.

The study has found that if a family living in an average sized house of six rooms increased the number of adolescents or adults by two, there would be a doubling in risk of meningococcal disease for any child living in the household. If the house had only four rooms then there would be almost a doubling of risk with the addition of just one extra adolescent or adult.

Statistics New Zealand census data shows that 75 percent of occupants living in crowded conditions are Maori and Pacific Island people, yet together these two groups form only 20 percent of New Zealand’s population. Young children are particularly affected, as almost 60 percent of crowded homes include children younger than five years of age, more than three times the average for New Zealand households. Census data for South Auckland, which has New Zealand’s highest rates of meningococcal disease, also shows the highest proportion of crowded homes of any urban area in New Zealand.

New Zealand is now in its tenth year of the meningococcal disease epidemic which is showing no signs of decreasing. ESR surveillance data show that the epidemic has now resulted in a total of 3300 cases and 150 deaths so the findings of this study clearly have implications for efforts to reduce meningococcal disease among children in New Zealand.

The most important preventive measure is to reduce household crowding which is also a major factor in the spread of other infectious diseases, as well as meningococcal disease. New Zealand has unusually high rates of rheumatic fever and tuberculosis, which are also linked to overcrowded housing. Since overcrowding is often associated with poverty, a key area to look at is the affordability of appropriate housing.

The study was carried out between 1997 and 1999 by a team of researchers from ESR, Auckland Health Protection Service, and the University of Auckland. It was jointly funded by the Health Research Council and Ministry of Health. It is the largest reported investigation of risk factors for meningococcal disease and the first carried out in New Zealand. It involved interviewing the parents of 202 Auckland children with meningococcal disease and a further 313 controls recruited door-to-door. It focused on children under eight years of age living in the Auckland region as they have the highest rates of this disease in New Zealand.

The Paediatric Infectious Disease Journal will be publishing the results in their October edition but the journal has approved pre-publication release of the findings because of their public health importance.

Contacts for further information:
Dr Michael Baker,
Public Health Physician, ESR
Phone (04) 237 0149 (w) (04) 237 2388 (direct dial) (04) 3858112 (h)

Professor Diana Lennon
Paediatrician, Middlemore Hospital
Phone (09) 276 0044 x 8329 (w) (021) 634 832 (mob)

Dr Nicholas Jones
Public Health Physician, Auckland Public Health Service
Phone (09) 262 1855 (w) (09) 376 1809 (h)

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