Natural Disasters and the Risk of Disease Epidemics

Following a natural disaster, the impacts can often be long-lasting, owing to damaged infrastructure, loss of agricultural land, businesses, and so on. A key concern also includes the sudden risk of disease epidemics, as vulnerability to disease increases after a disaster. Interestingly, vulnerability to natural hazards can also be exacerbated by disease - as well as other variables such poverty, conflict and population displacement (Basher, 2006). Developing countries are disproportionally affected as they lack resources, infrastructure, and disaster-preparedness systems (Watson et al., 2007).

The type of diseases that a natural disaster can exacerbate vary. After the 2004 Bangladeshi floods, contaminated drinking water caused the outbreak of diarrhoeal disease, found in over 17,000 cases (Watson et al., 2007). A large cholera epidemic (over 16,000 cases) was also noted in West Bengal in 1998 which was attributed to the preceding floods (Sur et al., 2000). Diseases such as tetanus and clusters of measles had spread following the 2005 Pakistan earthquake - particularly when routine vaccination coverage levels were low.

Pakistan earthquake 2005. Source

A common misconception is that diseases following a natural disaster are mostly spread from dead bodies, and thus this can lead to inappropriate burial of the dead without proper identification (Morgan, 2004). The most dangerous conditions are when dead bodies have contaminated water supplies; gastroenteritis being the most notable problem as corpses will commonly leak feaces - although communities will rarely use a water supply is they know it to be contaminated. Watson et al. (2007) argue that dead bodies can pose a serious health risk in a few situations that require specific precautions, such as deaths from cholera or hemorrhagic fevers. However (Morgan, 2004) contests this, stating that the causative agents in infections such as typhoid and cholera are unable to survive long in the human body following death, and therefore dead bodies pose little risk.

Rather, the main initiator of disease is reported to be displacement of a population following a natural disaster. This is due to overcrowding, limited water and sanitation supplies, and poor medical facilities which increase the risk of communicable disease transmission. The risk of outbreaks is associated with the size, health status and living conditions of the population displaced by the natural disaster.

Meterological events such as hurricanes, cyclones and flooding can affect vector breeding sites and vector-borne disease transmission (WHO, 2006). Standing water which is a result of heavy rainfall or overflow of rivers can create new breeding sites for mosquitoes. In a displaced population, there is an overcrowding of susceptible hosts coupled with a weakened health infrastructure and interruptions of ongoing disease control programmes, which contribute as risk factors for vector-borne disease transmission. Changing of habitats resulting from landslide deforestation, river damming and re-routing can also contribute to mosquito breeding.

As global environmental change is likely to exacerbate vulnerability to vector-borne diseases (e.g. malaria and cholera), it is important for disaster mitigation strategies to acknowledge the potential increase in secondary impacts such as disease epidemics resulting from hazards. Perhaps a most suitable solution, following this research, is to carry out effective strategies to avoid overcrowding when a population is displaced, and to provide more immediate substitute water and sanitation supplies to the effected population. What do you think is a suitable strategy to deal with disease outbreaks?