Second hand smoke exposure and the risk of invasive meningococcal disease in children: systematic review and meta-analysis. 2012, Murray, BMC Public Health

Passive smoking increases the risk of meningococcal infection by 2.2 times. When both parents smoke, the risk rises by a factor of 8. More: [1] [2] [3]
In Ghana, where meningococcal meningitis is much more common than in developed countries, cooking on wood-fired ovens increases the risk of disease is 9 times.