In the aftermath of a natural disaster, there's usually a breakdown in the infrastructure of the affected region: Roads may be impassable, telecommunications are rendered useless, electricity and other energy supplies are unavailable, and a general sense of malaise can easily creep in.
But does that mean an epidemic or other public health crisis is in the offing? You could be forgiven for thinking it's inevitable, since the popular notion of disaster zones as breeding grounds for all sorts of bacterial and viral contagion persists largely unchallenged. But a rigorous review of the facts in disaster zones reveals some interesting facts.
The Breakdown in Utilities and Infrastructure
When power supplies are cut off, safe food supplies and drinking water are imperiled. Water and wastewater plants are often offline, and a lack of refrigeration can cause food to spoil. According to a CDC report, this was the case in New York City after a 2003 blackout, when observers noticed a spike in diarrhea cases brought on by the consumption of spoiled food.
But in most disasters, infections and other diseases are held in check unless there is widespread dispersal of the population. When people are forced to flee an area after an earthquake, tsunami, flood or other natural or man-made disaster, a lack of safe food, clean drinking water and sanitation make the outbreak of disease a real risk.
The spread of communicable disease is much higher when displacement occurs because of war or other armed conflict. Indeed, some two-thirds of the deaths in war-torn areas has been blamed on communicable disease, according to the CDC. This is one of the most serious effects of war.
Dead Bodies After a Disaster
Perhaps the most persistent misconception about diseases following a disaster is the spread of diseases from dead bodies. These myths have been wildly exaggerated by news media and other uninformed sources.
In fact, there's almost no evidence that dead bodies help to spread disease, either in a disaster zone or in unaffected areas. Indeed, living bodies pose a much greater disease risk than the dead. The only exceptions to this are in areas where cholera or some kind of hemorrhagic fever is common, since those pathogens can spread from dead bodies.
A report from Haiti bears this out: After the devastating earthquake of 2010 struck the Caribbean island nation, journalists, military officials -- even Bill Clinton -- spoke alarmingly about the potential for an outbreak of disease, according to Popular Science.
The disease never occurred, however, until it was brought into the country from Asia several months after the earthquake, from U.N. peacekeeping forces who had arrived from Kathmandu. The soldiers were not properly screened for cholera after leaving Asia, and once they arrived in Haiti, the disease spread from their military base's primitive latrines into the waterways of Haiti.
Disasters and Disease Can Happen Anywhere
None of this should imply, however, that there are no diseases or public health problems associated with disaster zones. Indeed, the list of disease outbreaks following recent disasters is long and grim: Malaria in Costa Rica following a 1991 earthquake, leptosporosis in Argentina after a 1998 flood, hepatitis in 2005 after an earthquake in Pakistan and a Salmonella outbreak in Indonesia after flooding in 1992-93 are all, sadly, typical.
Though infectious diseases seem to be more common in developing countries after a disaster, it can happen anywhere. Severe diarrheal illness, norovirus, Salmonella and cholera were common in the United States after Hurricanes Katrina and Allison, the CDC reports, and most often seen in evacuees. And many cases of fungal coccidiomycosis occurred after the 1994 Northridge earthquake in Los Angeles, caused by airborne dust following quake-triggered landslides.
It's worth noting that many of these disease outbreaks were entirely preventable, but steps need to be taken before any disaster strikes to preclude the spread of illnesses. As the CDC points out, reacting after a catastrophe is too late: "The destruction of the preexisting public health infrastructure can aggravate (or eliminate) what may have been weak pre-disaster systems of surveillance and response."