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International notes Earthquake Disaster -- Luzon, Philippines

At 4:30 p.m. on July 16, 1990, an earthquake measuring 7.7 on the Richter scale struck northern and central Luzon Island in the Philippines, resulting in substantial morbidity and mortality and widespread damage. Among the areas severely affected were the mountain city of Baguio; the coastal areas in La Union; Dagupan city in Pangasinan; and the central plain area--primarily Cabanatuan city in Nueva Ecija and mountainous Nueva Viscaya. Buildings in Baguio and Cabanatuan suffered extensive structural failure, and buildings in the coastal areas in La Union and in Dagupan suffered foundation failure or the effects of liquefaction*. This report summarizes preliminary data gathered by Philippine Field Epidemiology Training Program (FETP) teams on the damage, deaths, and injuries sustained in the four areas. Baguio

The city of Baguio (1989 population: 154,000) covers 49 square kilometers (30 square miles) in the Cordillera mountains. Baguio is a major tourist destination and the principal trade and educational center in the Cordillera region. Twenty-eight buildings and 132 residences in the city were damaged or destroyed. Three hotels were totally destroyed. Two schools were severely damaged, trapping students and faculty members. A factory building collapsed and burned with workers trapped inside.

For the first 48 hours after the earthquake, the city was isolated from the rest of the country. Electric, water, and communication lines were destroyed. The city was inaccessible by land because of landslides and inaccessible by air, except to helicopters, because of damage at the airport. Food and fuel were scarce. Because hospital buildings were damaged, patients were relocated under tents set up in open spaces in front of hospitals. Damage to homes and the occurrence of many aftershocks caused most residents to set up camps in open spaces in the city. Three days after the earthquake, a main road leading to the city was cleared to enable delivery of supplies.

During the first 48 hours, rescue teams consisted of local volunteers, mainly miners and cadets from a military school in the city, who worked with their hands and with picks and shovels. Foreign rescue teams with sophisticated equipment and dogs trained for rescue were able to reach the area after 48 hours.

The FETP team estimated that 1084 earthquake-related casualties occurred: 695 injured survivors and 389 fatalities (case-fatality rate: 36%). The estimated injury rate was 703 per 100,000 population; the estimated death rate was 252 per 100,000.

The FETP team conducted a case-control study to identify risk factors for earthquake-related injuries. The study included 150 cases (surviving and deceased casualties) and 305 controls.** Casualties ranged in age from 3 months to 70 years (mean: 25 years); 51% were male. Eighty-four (56%) casualties were at home when the earthquake struck; 19 (13%), in school; 11 (7%), in a street; and 36 (24%), in other places. The majority (74%) of casualties were inside a building during the earthquake.

The 150 casualties sustained a total of 235 injuries (average: 1.6 injuries per person). The three most common injuries were contusion (35%), fracture (14%), and laceration (12%). The most common causes of injury were being hit by falling objects (37%), being crushed or pinned by heavy objects (29%), and falling (7%).

Based on preliminary analysis, cases and controls were similar in age and sex distribution. Similar proportions of cases and controls were inside (74% and 80%, respectively) and outside (26% and 20%, respectively) buildings during the earthquake. For persons who were inside a building, risk factors included building height, type of building material, and the floor level the person was on. Persons inside buildings with seven or more floors were 35 times more likely to be injured (odds ratio (OR)=34.7; 95% confidence interval (CI)=8.1-306.9). Persons inside buildings constructed of concrete or mixed materials were three times more likely to sustain injuries (OR=3.4; 95% CI=1.1-13.5) than were those inside wooden buildings. Persons at middle levels of multistory buildings were twice as likely to be injured as those at the top or bottom levels (OR=2.3; 95% CI=1.3-4.2). Cabanatuan

Cabanatuan (population: 176,053) is a major city in the central plain of Luzon. The city has many concrete buildings, mostly three stories high. The highest structure, a six-floor school, was the only building in Cabanatuan that collapsed during the earthquake. A total of 363 casualties (including 274 (75%) persons, primarily students, trapped in the collapsed school) were reported in Cabanatuan; 154 (42%) died. The death and injury rates were 87 and 206 per 100,000 population, respectively. Dagupan

Dagupan (population: 112,850) is a commercial city located along the coast of Lingayen Gulf. Approximately 150 concrete buildings were located in the commercial hub; most of these were less than five stories high. Approximately 90 (60%) buildings in the city were damaged, and approximately 20 collapsed. Some structures sustained damage because liquefaction caused buildings to sink as much as 1 meter (39 inches). Because the earthquake caused a decrease in the elevation of the city, several areas were flooded.

Of 64 casualties, 47 survived and 17 died. The injury and death rates were 57 and 15 per 100,000 population, respectively. Most injuries were sustained during stampedes at a university building and a theater. Fourteen (82%) of the deaths occurred among women. La Union

In La Union, a coastal province located in the northwestern part of Luzon, five municipalities (combined population: 132,208) were affected: Agoo, Aringay, Caba, Santo Tomas, and Tubao. Principal occupations are farming and fishing. The houses are constructed of wood, concrete, or light materials; most buildings are concrete and are less than four stories high. A total of 2387 families were dislocated when two coastal barangays (i.e., a large neighborhood or barrio) sank. Many buildings collapsed or were otherwise severely damaged. Of 493 casualties, 32 died. The injury and death rates were 349 and 24 per 100,000 population, respectively. Patterns of Damage

The earthquake caused different patterns of damage in different parts of Luzon Island. The mountain resort of Baguio was most severely affected, probably because it had the highest population density and many tall concrete buildings, which were more susceptible to seismic damage. Because all routes of communication, roads, and airport access were severed for several days, relief efforts were also the most difficult there. Relief efforts were further hampered by daily drenching, cold rains. Because Baguio is home to a large mining company and a military academy, experienced miners and other disciplined volunteers played a crucial role in early rescue efforts. Rescue teams arriving from Manila and elsewhere in Luzon were able to decrease mortality from major injuries. Surgeons, anesthesiologists, and specialized equipment and supplies were brought to the area, and victims were promptly treated. Patients requiring specialized care (e.g., hemodialysis) not available in the disaster area were airlifted to tertiary hospitals in metropolitan Manila. Outside of Baguio, destruction tended to be more diffuse. Damage was caused by landslides in the mountains and settling in coastal areas. Relief efforts in these areas were prompt and successful, partly because the areas remained accessible. Reported by: MC Roces, MD, NI Pastor, MD, IL Gopez, MD, MCL Quizon, MD, RU Rayray, MD, RR Gavino, MD, ES Salva, MD, MB Brizuela, MD, FC Diza, MD, EV Falcon, MD, JM Lopez, MD, MEG Miranda, DVM, RA Sadang, MD, NS Zacarias, MD, MM Dayrit, MD, Field Epidemiology Training Program, Philippines. Div of Environmental Hazards and Health Effects, Center for Environmental Health and Injury Control; Global Epidemic Intelligence Svc, Div of Field Svcs, Epidemiology Program Office, CDC.

Editorial Note

Editorial Note: As in previous earthquake disasters, the most important relief work in the Philippines was done by survivors during the first 48 hours after the shock (1,2). Because earthquake relief efforts may be hampered by a lack of accurate data (3,4), the Department of Health (DOH) deployed teams of FETP epidemiologists within 24 hours to each site to provide accurate estimates of casualties, damage, and needs.

Because Baguio was accessible only by air, setting priorities for relief shipments was vital. Daily reports were provided for local disaster coordinators and to headquarters in Manila. Information gathering was possible but was constrained by the lack of telephones, power, and transportation and by general confusion.

On July 19, 3 days after the earthquake, the priority of relief efforts shifted from treatment of injuries to public health concerns. For example, numerous broken pipes completely disrupted water systems, limiting the availability of potable water, and refugees who camped in open areas had no adequate toilet facilities. Early efforts at providing potable water by giving refugees chlorine granules were unsuccessful. Most potable water was distributed from fire engines, and DOH sanitarians chlorinated the water before it was distributed. Surveys of refugee areas showed few latrines; these had to be dug by the DOH.

Although national disaster plans had worked well in typhoons and floods, their effectiveness was undermined by the unprecedented demands caused by the earthquake. High-level government officials, such as cabinet secretaries and agency heads, were quickly assigned to manage emergency relief in different areas.

Important factors contributing to the risk for death after the collapse of buildings include entrapment, the severity of injuries, length of time victims can survive without medical attention, and time to rescue and medical treatment (5-7). Earthquake drills are important, particularly in relation to appropriate occupant behavior at the time of an earthquake (8). Deaths and injuries caused by stampedes in schools underlined the need for earthquake drills.

A widespread public expectation was that epidemics of communicable diseases would follow the earthquake. However, sentinel surveillance sites established in each of the earthquake areas did not detect increases in diarrhea, measles, or other diseases, confirming experiences after previous earthquakes (9). This information was released to the press frequently and helped to quell rumors, a major concern in the second and third weeks following the earthquake. In addition, reliable epidemiologic data permitted relief managers to avoid displacing important relief goods with unnecessary medicines (sorting and storing large quantities of inappropriate medicines has been a problem after other recent earthquakes (10)).

Many nations contributed effectively to the successful relief effort. The most useful international relief was low-technology assistance, such as tents, blankets, and food. Teams equipped with high-technology equipment to detect survivors arrived after most of the survivors had already been extricated. A team from Singapore remained for several weeks to provide a range of services, including medical care and cooking; these services were particularly useful. In addition, in response to a request from the Philippine FETP, the government of Mexico provided information based on its experience with the recent earthquake in Mexico; this information aided the Philippines in its public health response.

Future international relief efforts should focus more on problems that arise in the days after earthquakes. In Baguio, these needs were

  1. engineers to establish whether buildings are habitable and to help reestablish water and communication lines, 2) volunteers to help remove corpses from the wreckage, 3) psychologists and psychiatrists to attend to the psychological problems of helplessness, depression, and anger in survivors and rescuers, and 4) tents and food.


  1. Noji ER. The 1988 earthquake in Soviet Armenia: implications for

earthquake preparedness. Disasters 1989;13:255-62.

2. de Bruycker M, Greco D, Annino I, et al. The 1980 earthquake in southern Italy: rescue of trapped victims and mortality. Bull WHO 1983;61:1021-5.

3. Lechat MF. Disasters and public health. Bull WHO 1979;57:11-7. 4. Foege WH. Public health aspects of disaster management. In: Last JM, ed. Public health and preventive medicine. 12th ed. Norwalk, Connecticut: Appleton-Century-Crofts, 1986:1879-84.

5. Noji EK, Kelen GD, Armenian HK, Oganessian A, Jones NP, Silvertson KT. The 1988 earthquake in Soviet Armenia: a case study. Ann Emerg Med 1990;19:891-7.

6. Glass RI, Urrutia JJ, Sibony S, et al. Earthquake injuries related to housing in a Guatemalan village. Science 1977;197:638-43.

7. Noji EK, Armenian HK, Oganessian AP. Case control study of injuries due to earthquake in Soviet Armenia. Ann Emerg Med 1990;19:449.

8. de Bruycker M, Greco D, Lechat MF. The 1980 earthquake in Southern Italy: morbidity and mortality. Int J Epidemiol 1985;14:113-7.

9. Anonymous. The risk of disease outbreaks after natural disasters. WHO Chronicle 1979;33:214-6. 10. Autier P, Ferir M-C, Hairapetien A, et al. Drug supply in the aftermath of the 1988 Armenian earthquake. Lancet 1990;335:1388-90. *A change in the soil from a firm material into a viscous semiliquid material that resembles quicksand.

**A case was any casualty (injured or dead) resulting directly from the earthquake or aftershocks. For injured persons, information was obtained from the patients, when possible, or from other survivors; for infants and young children, from their parents or guardians; and for decedents, from survivors or from rescuers. Controls were noninjured family members or noninjured persons in refugee centers.

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