Epidemics After Natural Disasters Watson J, et al. Emerg Infect Dis. 2007;13:1–5.
The relationship between natural disasters and communicable diseases is frequently misconstrued. When death is directly due to a natural disaster, human remains do not pose a risk for outbreaks. Dead bodies only pose health risks in select situations that require specific precautions, such as death from cholera, shigellosis or hemorrhagic fevers. Risk for communicable disease transmission after disasters is associated primarily with the size and characteristics of the population displaced, proximity of safe water and functioning latrines, nutritional status of the displaced population, level of immunity to vaccine preventable diseases such as measles, and access to health care services.
Several types of communicable diseases have been associated with populations displaced by natural disasters. Diarrheal disease outbreaks can occur after drinking water that has been contaminated and have been reported after flooding and related displacement. Etiologic agents include Vibrio cholerae, enterotoxigenic Escherichia Coli, Salmonella enterica and Cryptosporidium parvum. Although the risk for diarrheal disease outbreaks following natural disasters is higher in developing countries than in industrialized countries, norovirus, Salmonella and toxigenic and nontoxigenic V. cholerae were confirmed among Hurricane Katrina evacuees in the United States.
Crowding is common in populations displaced by natural disasters and can facilitate the transmission of communicable diseases, e.g., measles and meningococcal meningitis. Acute respiratory infections are a major cause of illness and death among displaced populations, particularly in children less than 5 years of age. Acute respiratory infections accounted for the highest number of cases and deaths among those displaced by the tsunami in Aceh in 2004 and by the 2005 earthquake in Pakistan.
Natural disasters, particularly meterologic events such as cyclones, hurricanes and flooding can affect vector-breeding sites and vectorborne disease transmission. Malaria outbreaks in the wake of flooding are a well-known phenomenon. Although not directly associated with flooding, the risk for dengue outbreaks can be influenced by other complicating factors, such as changes in human behavior, movement to endemic areas, interruption in disease control activities and changes in habitat.
Other diseases associated with natural disasters include tetanus and coccidioidomycosis. A cluster of 106 cases of tetanus, including 20 deaths, occurred in Aceh and peaked 2 1/2 weeks after the tsunami. An outbreak of coccidioidomycosis was associated with exposure to increased levels of airborne dust subsequent to landslides in the aftermath of the 1994 Southern California earthquake.
Disaster-related interruption of services may disrupt water treatment and supply plants, increasing the risk for waterborne diseases. An increase in diarrhea illness in New York City followed a massive power outage in 2003. The outbreak investigation linked diarrhea illness with the consumption of meat and seafood after the onset of the power outage, when refrigeration facilities were widely interrupted.
Comment: Disaster-related deaths are overwhelmingly caused by the initial traumatic impact of event. Disaster preparedness plans should also take into account the health needs of the surviving disaster-affected populations. Five basic steps that can reduce the risk for communicable disease transmission in populations affected by natural disasters are summarized in an online table (Appendix Table, available from www.cdc.gov/ncidod/EID/13/1/1-appt.htm).