Guidelines
The following information has been extracted from the recently revised PAHO Scientific Publication No. 407. This revised version will be available for distribution by the summer of 1999.

Usually because of dwelling destruction, earthquakes may cause many deaths and injure large numbers of people. The toll depends mostly on three factors:

1. Housing type: Houses built of adobe, dry stone, or unreinforced masonry, even if only a single story high, are highly unstable and their collapse causes many deaths and injuries. Lighter forms of construction, especially wood-frame, have proved much less dangerous. After the 1976 earthquake in Guatemala, for example, a survey showed that in one village with a population 1,577, all of those killed (78) and severely injured had been in adobe buildings, whereas all residents of wood frame buildings survived.
2. Time of day at which the earthquake occurs: Night occurrence was particularly lethal in the earthquakes in Guatemala (1976) and Bolivia (1998), where most damage occurred in adobe houses. In urban areas with sound housing but weak school or office structures daytime occurrence results in higher death rates.
3. Population density: the total number of deaths and injuries is likely to be much higher in densely populated areas. There are large variations within disaster-affected areas. Mortality of up to 85% occasionally may occur close to the epicenter of the earthquake. The ratio of dead to injured decreases as the distance from the epicenter increases. Some age groups are more affected than others are; fit adults are spared more than small children and the elderly, who are less able to protect themselves. However, 72% of the deaths resulting from collapsed buildings in the 1985 Mexico earthquake comprised those between the ages of 15 and 64.

Secondary disasters

Secondary disasters may occur after earthquakes and increase the number of casualties requiring medical attention. Historically, the greatest risk is from fire, although in recent decades, post-earthquake fires causing mass casualties have been uncommon.

Kinds of Injuries

Little information is available about the kinds of injuries resulting from earthquakes, but regardless of the number of casualties, the broad pattern of injury is likely to be a mass of injured with minor cuts and bruises, a smaller group suffering from simple fractures, and a minority with serious multiple fractures or internal injuries requiring surgery and other intensive treatment.

Demand for health services

Demand for health services occurs within the first 24 hours of an event. Injured people may continue to appear at medical facilities only during the first three to five days, after which presentation patterns return almost to normal. Patients may appear in two waves, the first consisting of casualties from the immediate area around the medical facility and the second of referrals as humanitarian operations in more distant areas become organized.