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A large outbreak of Q fever in the West Midlands: windborne spread into a metropolitan area?
J I Hawker1, J G Ayres, I Blair
1Department of Public Health Medicine, East Birmingham Health Authority. jhawker@cdscwmid.demon.co.uk
Abstract:
The largest outbreak of the zoonotic disease Q fever recorded in the United Kingdom (UK) occurred in Birmingham in 1989. One hundred and forty-seven cases were identified, 125 of whom were males, and 130 of whom were between 16 and 64 years of age. Fewer cases of Asian ethnic origin were observed than expected (p < 0.01), and more smokers (p < 0.005). A case control study (26 cases and 52 matched controls) produced no evidence that direct contact with animals or animal products had caused the outbreak. The epidemic curve suggested a point source exposure in the week beginning 10 April. The home addresses of cases were clustered in a rectangle 11 miles (18.3 km) north/south by 4 miles (6.7 km) east/ west, and attack rates became lower towards the north. Directly south of this area were farms engaged in outdoor lambing and calving, a potent source of coxiella spores. A retrospective computerised analysis showed that the geographical distribution of cases was associated with a source in this area (p < 0.00001). On 11 April, unusual southerly gales of up to 78 mph (130 km/h) were recorded. The probable cause of the outbreak was windborne spread of coxiella spores from farmland to the conurbation.
Insights
The 1989 Birmingham Q fever outbreak, the UK's largest, was likely caused by windborne Coxiella burnetii spores from nearby farms. This zoonotic disease spread rapidly through the urban environment.
Area of Science:
- Epidemiology
- Zoonotic Diseases
- Environmental Health
Background:
- The United Kingdom experienced its largest recorded outbreak of the zoonotic disease Q fever in Birmingham in 1989.
- The outbreak affected 147 individuals, predominantly males aged 16-64.
- Observed lower-than-expected cases among Asian ethnic groups and higher rates among smokers.
Purpose of the Study:
- To investigate the cause and transmission dynamics of the 1989 Birmingham Q fever outbreak.
- To identify potential sources and exposure pathways for Coxiella burnetii.
Main Methods:
- Case-control study involving 26 cases and 52 matched controls to assess direct animal contact.
- Epidemic curve analysis to determine exposure timing.
- Geographical analysis of case distribution and retrospective computerised analysis linked to potential environmental sources.
- Meteorological data analysis, including wind speed and direction.
Main Results:
- Case-control study found no evidence linking direct animal contact to the outbreak.
- Geographical analysis revealed a cluster of cases north of farms engaged in lambing and calving.
- Retrospective analysis confirmed a strong association between case distribution and a source in the farming area (p < 0.00001).
- Unusual southerly gales on April 11th coincided with the probable exposure period.
Conclusions:
- The outbreak was likely caused by windborne spread of Coxiella burnetii spores from farmland to Birmingham.
- Environmental factors, specifically wind patterns and proximity to livestock, played a crucial role in the zoonotic disease transmission.