MlATTERS ARISING Epidemiological surveillance of diseases fillowing the earthquake of 23rd Novem- ber 1980, in Southern Italy: Discussion Whilst the international community waits with bated breath for the coming San Francisco earthquake, the level of scientific interest in seismic disasters continues to increase. Each new catastrophe stimulates further research and new expertise. seemingly in proportion to the scope and profundity of the event. Thus, the Prince William Sound, Alaska, earthquake of 1964, one of the largest this century, gave rise to an eight-volume history (Committee on the Alaska Earthquake, 1973) and many new theories about seismic effects. But as it occurred in a sparsely populated area killing only 115 people and seriously injuring less than 50 others. the Alaska earthquake added relatively little to present knowledge of disaster epidemiology. On the other hand, the earthquake which occurred in Southern Italy on 23rd November 1980, seriously affected a large and heterogenous population and thus provided an important opportunity for disaster epidemiologists. The account of epidemiological work after the Italian disaster by Greco et al. (Disasters 5(4), 398-406) is a very welcome addition to a field in which the literature and documentation are mostly recent or limited (see, for instance, Beinin, 1981; Solomons and Butte, 1978; Whittaker et al., 1974), and where there is still ample scope for new experience to suggest modifications to existing procedures (see Spencer et al., 1977). The main conclusions of this new paper - first, that the earthquake had remarkably little effect on the incidence of selected diseases, and secondly that there is a relationship between mortality or morbidity rates and the degree of seismic damage to settlements - are not in doubt. However, a number of observations made by Greco et al. require further qualification; for example, concerning the accuracy of statistics. the role of the press and the methodology used in epidemiological calculations. The present writer is con- cerned that the proper lessons be learnt from the 1980 disaster - especially in terms of the methods of analyzing epidemiological data - so that if future earthquake catastrophes give rise to serious epidemics, or patterns of mortality and morbidity that are difficult to interpret, the experience gained from the Italian Disaster will be used effectively. Accordingly, the following comments summarize some points of contention over the use, interpretation and reliabilit Y of statistics associated with disaster, the role of the pre\\ with respect to rumours of epidemics, and the interpretation of mortality and morbidity statistics. MAGNITUDE OF THE DISASTER - BASIC STAT- ISTICS Epidemiological surveillance after a disaster must necessarily begin by defining the nature of the event (its magnitude, scope, spatial boundaries, and so on) and relevant characteristics of the affected population (num- bers, density, degree of concentration in urban centres, death and injury rates, percentage homelessness, etc.). To accomplish this aim, Greco et al. rely on disaster statistics published by the Italian Government’s Special Commission for the Earthquake-Affected Area (Commissario speciale per le zone terremotati - the Zamberletti Commission - 25th November 1980, and thereafter). But there is a serious problem of accuracy associated with such statistics. Table 1 gives some estimates of the effect of the disaster, based on information periodically released to the press and regional administrations of the disaster zone by the Zamberletti Commission; and it appears as if there is no stable estimate of the number of victims, homeless people and affected settlements. The problem is twofold: first, it is difficult to estimate the precise number of deaths and injuries - and the precise amount of damage - which is directly attributable to the earthquake; and, secondly, it is difficult to establish a stable figure for volatile and changeable factors such as the number of homeless people. In the City of Naples, for example, the number of homeless was initially estimated at 15,161 (I1 Mattino, Naples daily newspaper, 4th December 19801, but rose to 178,000 after 46,440 structural surveys had been carried out, resulting in a large number of evacuations (I1 Mattino, 3rd March 1981). These totals probably include an indefinite number of people whose homelessness was caused by factors other than the earthquake (for example, unemployment or poverty). The number of affected communities was given by the Zaniberletti Commission as 315 (Greco et al., 1981). but a total of 561 comuni (basic administrative ‘parishes’) reported significant damage (Alexander, 1982). One feels that the toll of deaths and injuries caused by the disaster might just as well have been obtained by subtracting the pre-disaster figures (seasonally averaged) from the overall total of deaths and injuries caused during the impact period of the disaster, thus leaving a residual or “excess” number of casualties to be attributed to the catastrophe. Any estimate of mortality and morbidity rates, or of the extent ofthe area that was significantly afiected by the earthquake, should bear these problems in mind, and it is disappointing that Greco et al., do not present a full discussion of the data base on which their analysis of mortality and morbidity associated with the disaster is based. The role of the press Creco et al. give the impression that the Italian news media were quick to dramatize the disaster by spreading 149
Transcript
MlATTERS ARISING
Epidemiological surveillance of diseases fillowing the earthquake of 23rd Novem- ber 1980, in Southern Italy: Discussion
Whilst the international community waits with bated breath for the coming San Francisco earthquake, the level of scientific interest in seismic disasters continues to increase. Each new catastrophe stimulates further research and new expertise. seemingly in proportion to the scope and profundity of the event. Thus, the Prince William Sound, Alaska, earthquake of 1964, one of the largest this century, gave rise to an eight-volume history (Committee on the Alaska Earthquake, 1973) and many new theories about seismic effects. But as it occurred in a sparsely populated area killing only 115 people and seriously injuring less than 50 others. the Alaska earthquake added relatively little to present knowledge of disaster epidemiology. On the other hand, the earthquake which occurred in Southern Italy on 23rd November 1980, seriously affected a large and heterogenous population and thus provided an important opportunity for disaster epidemiologists.
The account of epidemiological work after the Italian disaster by Greco et al. (Disasters 5(4), 398-406) is a very welcome addition to a field in which the literature and documentation are mostly recent or limited (see, for instance, Beinin, 1981; Solomons and Butte, 1978; Whittaker et al., 1974), and where there is still ample scope for new experience to suggest modifications to existing procedures (see Spencer et al., 1977). The main conclusions of this new paper - first, that the earthquake had remarkably little effect on the incidence of selected diseases, and secondly that there is a relationship between mortality or morbidity rates and the degree of seismic damage to settlements - are not in doubt. However, a number of observations made by Greco et al. require further qualification; for example, concerning the accuracy of statistics. the role of the press and the methodology used in epidemiological calculations. The present writer is con- cerned that the proper lessons be learnt from the 1980 disaster - especially in terms of the methods of analyzing epidemiological data - so that if future earthquake catastrophes give rise to serious epidemics, or patterns of mortality and morbidity that are difficult to interpret, the experience gained from the Italian Disaster will be used effectively. Accordingly, the following comments summarize some points of contention over the use, interpretation and reliabilit Y of statistics associated with disaster, the role of the pre\\ with respect to rumours of epidemics, and the interpretation of mortality and morbidity statistics.
MAGNITUDE OF THE DISASTER - BASIC STAT- ISTICS
Epidemiological surveillance after a disaster must necessarily begin by defining the nature of the event (its magnitude, scope, spatial boundaries, and so on) and relevant characteristics of the affected population (num- bers, density, degree of concentration in urban centres, death and injury rates, percentage homelessness, etc.). To accomplish this aim, Greco et al. rely on disaster statistics published by the Italian Government’s Special Commission for the Earthquake-Affected Area (Commissario speciale per le zone terremotati - the Zamberletti Commission - 25th November 1980, and thereafter). But there is a serious problem of accuracy associated with such statistics. Table 1 gives some estimates of the effect of the disaster, based on information periodically released to the press and regional administrations of the disaster zone by the Zamberletti Commission; and it appears as if there is no stable estimate of the number of victims, homeless people and affected settlements.
The problem is twofold: first, it is difficult to estimate the precise number of deaths and injuries - and the precise amount of damage - which is directly attributable to the earthquake; and, secondly, it is difficult to establish a stable figure for volatile and changeable factors such as the number of homeless people. In the City of Naples, for example, the number of homeless was initially estimated at 15,161 (I1 Mattino, Naples daily newspaper, 4th December 19801, but rose to 178,000 after 46,440 structural surveys had been carried out, resulting in a large number of evacuations (I1 Mattino, 3rd March 1981). These totals probably include an indefinite number of people whose homelessness was caused by factors other than the earthquake (for example, unemployment or poverty). The number of affected communities was given by the Zaniberletti Commission as 315 (Greco et al., 1981). but a total of 561 comuni (basic administrative ‘parishes’) reported significant damage (Alexander, 1982).
One feels that the toll of deaths and injuries caused by the disaster might just as well have been obtained by subtracting the pre-disaster figures (seasonally averaged) from the overall total of deaths and injuries caused during the impact period of the disaster, thus leaving a residual or “excess” number of casualties to be attributed to the catastrophe. Any estimate of mortality and morbidity rates, or of the extent ofthe area that was significantly afiected by the earthquake, should bear these problems in mind, and it is disappointing that Greco et al., do not present a full discussion of the data base on which their analysis of mortality and morbidity associated with the disaster is based.
The role of the press
Creco et al. give the impression that the Italian news media were quick to dramatize the disaster by spreading
149
150 MATTERS ARISING
Table 1. Various published estimates of the effect of the 1980 earthquake
Dead Missing Injured Homeless Affected comuni
Reported information 3,004 1,485 7,418 170,000 179 2nd December 1980
Tally of all
1st December 1980
Published estimate 2,909 8,197 480,628 85+ 1 st December 1980
Published total 2,998 8,245 234,%0 4 7 5 6 4 9 1st March 1980 Alexander (1982) 3,007 9,394 270,255 561
Greco et al. (1 98 1) 2,459 7,513 315
published information 3,435 7,690 329,945 306
Source: adapted from Alexander (1982, p. 82-84).
“rumours of epidemics of every type’’ (Greco et al,, 1981, p. 3981, but in the present author’s estimation this is not a fair judgement. In general, press reporting was sober, responsible and detailed, and placed particular emphasis on the presentation of data relating to death, injury, honielessness, damage and disease outbreaks without attempting to exaggerate them. This is particularly true of the two daily newspapers published in central-southern Italy, where the earthquake occurred cI1 Mattino of Naples and La Gazzetta del Mezzogiomo of Bari). However, both papers occasionally gave false information on epidemiol- ogical matters - for example, of the placing of a sanitary cordon around the severely damaged town of Conza di Canipania (Province of Avellino) six days after the earthquake (see II Mattino, 29th November 1980). The cordon was never actually set up.
Whilst the present author would not dispute that there were rumours of epidemics during the aftermath of the disaster (cf. Greco et al., 1981, p. 405; “Alarm over the health situation,” IIMuttino, 4th December 1980; “Fears of epidemics in the Spring,” I1 Mattino, 3rd April 19811, there are certain positive aspects in the press response. For cxaniple, the recognition that most diseases have definable incubation periods, and some outbreaks which occurred directly after the disaster or after subsequent changes towards colder or warmer weather therefore could not have been provoked by such events (see I1 Mattino, 1st April 1981).
One additional problem is that few medical officials who were interviewed by newspaper reporters during the aftermath of the disaster were willing to state categorically that there was no risk of disaster-related epidemics. Furthermore, it was not until eight days after the earthquake that a comprehensive, fully co-ordinated medical and sanitary plan emerged (“A sanitary plan is ready but it doesn’t begin: too much confusion,” La
Gazzetta del Mezzogiomo, 28th November 19801, and the interim period was characterized by lack of precise guidance, such that the local medical personnel who were interviewed by the press had insufficient information on the actual risk of disease epidemics or the degree of preparedness against them. As Greco et al. observed, the epidemiological surveillance network did not tunction during the first two weeks after the disaster, and thus much important information on factors such as the initial total ot hospital admissions, trauma cases, surgical cases, and so on, was lost. More discussion of these problems by Greco r q al., would again be welcome.
The final point to be noted about the role of the press concerns how far published rumours of epidemics stimulated a wasteful and ineffective response on the part ot the medical authorities - for example, mass-vaccination. In this context, there is another factor to be considered: the arrival in the disaster area of a large quantity of drugs and vaccines may have created the incentive to use them in prophylactic measures. Here, allegations that the major drug-producing companies were “dumping” vaccines in the disaster area (my sources here are confidential) need to be investigated before the response to rumours can be properly gauged.
QUANTITATIVE PROBLEMS Whilst the programme of epidemiological surveillance
after the disaster is clearly presented by Greco rt ul., their data analysis procedures require much more clarification. According to these authors, a Fortran computer program was written in order “to describe the spatial and temporal patterns in the incoming data” (Greco et al . . 1981. p. 098). I t is thus regrettable that they made no further mention of the spatial patterns-ven to the extent of a brief comment on their lack of significance, if they actually demonstrate very little. With the exception of macroseismic intensity
MAlTERS ARISING 151
Table 2. Calabria and Basilicata, southern Italy: Monthly data on the incidence per 100,OOO population of selected diseases, July 1978 - October 1980 (pre-disaster) and
Upper Lower Regression intercept (a) Regression slope (b) Standard error of Yon X t-statistic for (b) Significance level
Post earthquake data:
n Mean
Test of difference of means:
t(pre. post) Y (degrees of freedom) Significance level
28 5.438 0.808
3.85 7.02 5.72 -0.021 0.78 -1.10 n.s.t
7 4.859
1.84 33 n.s.
24 5.375 0.321
4.75 6.00
4.10 29 0.01
28 1.502 0.648
0.23 2.77 1.99 -0.036 0.57 12.64 0.05 *
7 1.075
1.66 33 n.s.
24 1.396 0.336
0.74 2.06
2.26 29 0.05
28 0.984 0.232
0.53 1.44 0.95 0.003 0.23 0.51 n.s.
5 1.025
- 0 . 2 9 31 n.s.
24 0.973 0.099
0.78 1.17
- 0 . 4 7 27 n.s.
28 0.094 0.050
4 . 0 1 0.19 0.09 0.001 0.05 0.55 n.s.
7 0.109
-0.71 33 n.s.
24 0.095 0.035
0.03 0.16
-0.86 29 n.s.
Smoothed using 5-month moving average (MA) filter. tn.s. is not significant. %.e. decline in incidence rate is significant at the 95% level
*
surveys (Borcherdt, 1975) and the mapping of “tectonic provinces” (Kerr, 1978) spatial models of the effects of earthquakes are rare, and there is thus a great need to know how such effects are distributed across a disaster area (see Foster, 1980, Chapter 5; UNESCO, 1978) - especially in view of the inevitable spatial differences in demand for aid assistance and medical services.
With respect to the temporal data there are problems of a different kind, Greco et al. present no less than 13 different graphs on the weekly incidence of different disorders, diseases and symptoms occurring in the surveillance area (plus the total number of medical cases, hospital admissions and surgical cases) for 28 weeks after the disaster. But they do not describe the pre-disaster incidence rates to the extent that they can be compared with the figures obtained during the aftermath. All data on disaster epidemiology should be directly cwnipared with incidence rates that might have been expected i n the absence of the disaster (which are usually
taken to be the seasonally-averaged rates for an appropriate catchment area). For monthly observations, a five month, centrally weighted moving average applied over several years’ data would seem an acceptable way of generalizing such data before calculating monthly means: in the case of weekly daya a longer moving average would probably be more appropriate.
Table 2 shows some statistical calculations based on raw and smoothed runs of the data for four of the diseases analyzed by Greco et al. (data from ISTAT (1978-1981)). These statistics give rise to the following observations:
1. Even after smoothing, the pre-earthquake data show a wide variability (see standard deviations and 95% confidence limits of means) making it difficult to estimate mean values with any degree of precision.
2. During the 28 months prior to the earthquake there had been a significant decline in the incidence per
I52 MATTERS ARISING
IO0.OOO of typhoid fever. Viral hepatitis, paratyphoid and meningococcal meningitis rates had remained stable in Canipania and Basilicata. Analysis of post- earthquake tendencies should bear these trends in in i nd .
3 . Comparison using the smoothed pre-earthquake data suggests that the incidence rates of viral hepatitis and typhoid fever were significantly lower during the after- math of the disaster (at the 99 and 95% levels, respectively): this may, however, be merely a seasonal effect. 'The other incidence rates were unaffected by the disaster.
? * 1 he approach described above may be a more rigorous way of comparing the pre- and post-disaster data than that employed by Greco et al. (1981, p. 4001, who used a Chi-square test. Estimating Chi-square frequencies depends upoit all observations being independent of each other, whereas a disease epidemic would tend to create statistical autocorrelation among weekly or monthly data, biasing the independence of observed Chi-square frequencies (cf. Spiegel. 1961, Chapter 12).
CORRELATION OF MORTALITY AND MORBIDITY RATES WITH DEGREE OF SEISMIC DAMAGE
The availability of comprehensive data on death and injury rates, and on the degree of damage to communities rcsulting from the disaster, means that it is now possible to expend the scope of observations on these factors made by Greco r'r a l . , and to give these observations a predictive,
rather than merely a descriptive, capability. Unfortunately. however, one must continue to bear in mind that the definition of injury for record purpqses has never been given by the Italian government commission who released the data, and that differing criteria may have gone in to assessing the severity of damage from settlement 10
settlement. One of the most comprehensive analyses of earthquake
damage effects in general was carried out by Page, Blume and Joyner (19751, who also correlated damage in million U.S.S) with death totals for 15 major earthquake disasters occurring over the period 1906-1973 (Page et al . , 1075, 1). 606). Reworking these data suggests that the relationship between death rates and damage is tenuous at the scale ol overall totals: for the 15 disasters listed by Page, Blume ant1 Joyner the coefficient of determination, R 2 , is 0.233, wi th an associated F value which is significant at the 95 but not the 99% level; and for the 9 of those disasters that occurred in the U.S.A. the R 2 is 0.491, which is again only significant at the 95% level. However, analyzing all available data on deaths, injuries and percentage damage to urban centres resulting from the 1980 Italian earthquake suggests that some fairly strong relationships may exist between each of these factors, within the scope of at1
individual seismic disaster (see Table 3). In this sense, the conclusions derived from the pilot study
carried out by Greco et al. are confirmed by analysis ot' the entire data set, except that the correlation between injuries/ 1 ,OOO population and percentage damage is somewhat weaker when the death rate is considered as a partial variable (i.e. a small proportion of the variation in injury
Table 3. Correlations among deaths/ 1 ,OOO, recorded injuries/ 1,OOO and percentage damage in all communities
Data from Regione Basilicata (1981). tData from Provincia di Napoli (1981). *
MATTERS ARISING 153
rates from place to place is associated directly with variations in death rates - presumably involving some other mutually causative factor - rather than with the severity of damage). Further analysis has shown that although removing the provincial and regional capitals from the data set affects the incidence rates of death and injury, it does not affect the significance of correlations.
For all settlements where deaths and injuries occurred the mean ratio is 0.39, but the standard deviation of this value dictates that the true mean could have occurred anywhere in the range 0.30-0.48, with 95% confidence in the estimate. The moment coefficient of skewness, at 2.81, is highly positive or right skewed, indicating a wide range of high values (in other words, a wide variety of instances where the death toll was high relative to the number of recorded injuries); but the moment coefficient of kurtosis, which at 12.66 is highly leptokurtic, indicates that many values of the deaths/ injuries ratio differed little from the mean. Thus any replication of the conditions giving rise to the data analyzed above might generate a mean deathdinjuries ratio of between 1:2.08 and 1:3.33, derived from many similar values which are close to the mean, and a number of cases where dcaths exceed the expected proportion relative to injuries h y a substantial and highly variable amount.
CONCLUSIONS
Although the 1980 Italian earthquake disaster provoked no great outbreaks of disease and gave rise to patterns of mortality and morbidity that were very much in line with previou\ experience (PAHO, 1981), study of the epidemiol- ogy of the disaster will prove extremely useful to the managenlent of casualties and potential outbreaks of disease I\ hich will inevitably occur in similar disasters in the future. I t I \ thus extremely important to ensure. not only that epidemiological surveillance is sufficiently coniprehen- sive, but that the subsequent analysis of data i5 thorough and rigoiou\. I t is hoped that the above comments have aired sonic of the problems of conducting such analyses, in order th.rt we may be better prepared to meet the needs imposed hq the next earthquake disaster.
David Alexander
Department of Geology and Geography University of Massachusetts Amherst, MA 01003, U.S.A.
major earthquakes in Russia, Disasters 5(4), 142-146 ( I 98 1).
Borcherdt R.D. (Editor), Studies ojSeismic Zonation of the Sun Francisco Ba-y Region, 102 pp. United States Geological Survey Professional Paper No. 941-A (1975).
Committee on the Alaska Earthquake, The Great Alaska Earthquake o f f 964,8 Volumes. National Research Council (National Academy of Sciences), Washington, D.C. (1973).
Foster H.D., Disaster Planning, 275 pp. Springer-Verlag, New York (1980).
Greco D. et al., Epidemiological surveillance of diseases following the earthquake of 23rd November 1980, in southern Italy, Disasters 5(4), 39-06 (1 981).
I.S.T.A.T., Bollettino mensile d i stutistica. Istituto Centrale di Statistica, Rome (monthly bulletin and annual summar- ies) (1978-1981).
Kerr R.A., U.S. earthquake hazards: real but uncertain in the East. Science 201, 1001-I003 (15th September 1978).
Page R.A., Blume J.A. and Joyner W.B., Earthquake shaking and damage to buildings, Science 189, 6 0 1 6 0 8 (22nd August 1975).
P.A.H.O., Emergency Health Management Ajier Natural Disaster. 67 pp. Scientific Publication No. 407, Pan American Health Organization/ World Health Organ- ization, Washington. D.C. (1981).
Provincia di Napoli, Ricostruire dopo la catastrofe, 112 pp. Provincial Administration, Naples (March 1981).
Regione di Basilicata, Dal bilancio di un sisma ui programmi d i ricostruzione e sviluppo, 64 pp. Fascicolo della Regione di Basilicata, Potenza (February 1981).
Solomons N.W. and Butte N., A view of the medical and nutritional consequences of the earthquake in Guatemala, lnirrnational Health 93(2). 161 -1 69 (1 978).
Spencer H.C. et al., Disease surveillance and decision- making after the 1976 Guatemala earthquake, Luncet 2 , 181-184 (23rd July 1977).
Spiegel M.R., Statistics. Schaum's Outline Series, 359 pp. McGraw-Hill, New York (1961).
REFERENCES
Alexander D.E., The Earthquake of 23rd November 1980. in Campania and Basilicata, Southern Italy, 164 pp. International Disaster Institute/Foxcombe Publications, London ( 1982).
Beinin L., A n examination of health data following two
UNESCO, The Assessment and Mitigation of Earthquake Risk. Natural Hazards, 341 pp. United Nations Education- al, Scientific and Cultural Organization, Paris (1 978).
Whittaker R. et al., Earthquake disaster in Nicaragua: reflections on the initial management of massive casualties. I . Truuma 14(1), 37-43 (1974).
