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close this bookEpidemiologic Surveillance after Natural Disaster (PAHO - OPS; 1982; 105 pages) [FR] [ES]
close this folderPart 1 : Epidemiologic surveillance and disease control after natural disaster
close this folderChapter 3 : Setting up surveillance systems
View the documentSurveillance of diseases between disasters under normal conditions
View the documentSurveillance sources following disaster
View the documentDiseases to include in the surveillance
View the documentThe collection, interpretation and utilization of data
View the documentProviding feedback to the field from the central level

The collection, interpretation and utilization of data

Participation of field health units in the surveillance system must be as complete as possible after a disaster. It is critical to motivate reporting units. The participation of predisaster units should be continued when possible, with emphasis in reporting placed upon the diseases or symptom complexes targeted for surveillance. Public health nurses and inspectors have proven to be valuable reporting sources in the Caribbean. Health teams mobilized for the relief effort should be adequately briefed about the importance of surveillance, and should be given the case definitions to be used and be amply provided supplies of reporting forms. Briefing is ideally undertaken by the epidemiologist before the teams depart for the field. In practice, however, and usually for the investigation of rumors of epidemics, the surveillance system is often initiated once the teams are already in place. Visits by the epidemiologist to field units is psychologically beneficial and provides feedback and stimulates reporting.

Figure 2: Representative Form for Daily Report of Disease Surveillance Postdisaster Surveillance

Daily Report by (Name of Reporter) ___________________
For___________________
Date___________________

From___________________

Evacuation Center
Hospital OPD
Health Center
Clinic
Other Specify___________________

Location Address___________________

Phone No.___________________

NUMBER OF NEW CASES WITH

TOTAL

(1) Fever ( 100°F + 38°C + )

_______

(2) Fever and Cough

_______

(3) Fever and Diarrhea

_______

(4) Vomiting and/or Diarrhea

_______

(5) Fever and Rash

_______

(6) Other New Medical Problems Specify

_______

COMMENTS

COMPLETE FOR EVALUATION CENTER ONLY
No. of persons accommodated today

Report significant changes in Sanitation/Food Supply Situation

NOTE: COMPLETE BACK PORTION OF THE FORM FOR FIRST REPORT ONLY.

Two operational aspects of data collection deserve emphasis. First is the importance of regularly sending "negative" reports whenever no patients with notifiable diseases are seen in a unit. A report form with a line of zeros provides valuable information. It also permits assessment of the number of units participating in the surveillance system. Failure to report, on the other hand, can either mean a lack of disease, or that a unit has dropped out of the surveillance effort.

Speed of reporting, always critical in communicable disease surveillance, is especially vital following disaster. Mail and telephone services are most likely to be interrupted or erratic at that time. In general, weekly reporting from all units by telephone, telegraph or shortwave radio is preferable to reporting by mail. Immediate consultation about any unusual condition or suspected epidemic, at any time during the week, should be encouraged. Clear instructions about how to reach the central epidemiologist should be provided to workers in the field.

Innovative ways to facilitate rapid reporting during the period of severe disruption in transportation and communication should be sought by members of the epidemiology unit. This will frequently involve utilizing other elements of the relief effort. Previous sensitivity of the relief coordinator and national authorities to the importance of adequate surveillance for an effective overall effort will pay dividends. Example procedures used with success in previous disasters include daily or weekly radio reporting of selected diseases from the field; the distribution and retrieval of reporting forms by members of the drug and/or food distribution system; gaining access to the national security force's communication network; incorporating disease surveillance into a more general regular report required by the relief' coordinator; and regular visiting to field units by the epidemiologist or a member of the surveillance team.

Reporting units should be made to understand that the primary responsibility is theirs to collate and interpret weekly totals, and to act on the information they collect through surveillance. The epidemiologist, rather than being bureaucratically annoying, should help reporting units efficiently carry out these tasks in a standardized fashion. The epidemiologist should also be available for consulting about the diagnosis and management of infectious diseases with the antibiotics or biologics available, to investigate suspected outbreaks and to supervise the disease control efforts. In a well run surveillance effort it is not acceptable to passively report the appearance of measles or fever-bloody diarrhea in a population by mail. When this occurs, the situation gets out of control before the epidemiologist is aware of the problem.

It is also imperative that incoming notifications are evaluated immediately upon receipt by the epidemiology unit, rather than at the end of the reporting period. This will permit prompt response to rumors or enquiries, recognition of unusual reports (e.g., typhus, human rabies) and comparison of individual units of the current reporting period with previous ones. It will also make it possible to recognize sudden increases in more common conditions such as diarrhea and acute respiratory illness.

There should be a firm and immutable deadline established by the epidemiology unit for receipt of notifications before the daily and weekly tabulations are compiled. The unit frequently works twenty-four hour shifts immediately after a major disaster strikes. Under less urgent conditions or in long term relief efforts, the reporting week should end on Friday, notifications received on Monday and the weekly report completed Tuesday. In long term refugee camps, it has sometimes been necessary to resort to clinic reporting only one day per week in order to reduce the bookkeeping demand placed on field workers. These pragmatic changes do not, however, change the need for immediate reporting of epidemics or unusual cases of disease.

A firm deadline for weekly tabulations is required to ensure prompt evaluation and action. The epidemiologic week actually decided upon is of minor importance, but its scheduling should be agreed upon by national and relief epidemiologists to avoid confusion about actual case counts in formal reports. For instance, if a case of malaria is reported by the national group in week 30 and in week 31 by the relief effort, the question is raised of whether one or two cases existed. Disagreement on this rather trivial point has in the past been a source of friction in international relief where epidemiologists of the donor and host countries differ in what constitutes an epidemiologic week.

Figure 3, derived from Figure 2, is a model for a weekly tabulation report at the central level. This model entails a summary sheet in which disease in children (under 15 years) and adults (15 years and older) are separately notified and combined totals are given. In this model, cases and deaths are combined in a total notification because the central summary sheets should be kept as uncluttered as possible for easy scanning. Of course, deaths can be followed on a separate weekly summary sheet. Diseases not singled out for postdisaster surveillance should be tabulated on the regular weekly report form presented in Figure 1.

Figure 3: Representative Form for Weekly Summary of Central Epidemiological Surveillance



Fever ( 100°F + 38°C +)

Fever and Cough

Fever and Diarrhea

Vomiting and/or Diarrhea

Fever and Rash

Other New Medical Problems Specify ...



Reporting Unit

Disease

>15
Yrs
Old

<15
Yrs
Old

>15
Yrs
Old

<15
Yrs
Old

>15
Yrs
Old

<15
Yrs
Old

>15
Yrs
Old

<15
Yrs
Old

>15
Yrs
Old

<15
Yrs Old

>15
Yrs
Old

<15
Yrs
Old

Total
>15 Yrs
Old

Combined Total

COMMENTS

Weekly Report by (Name of Reporter) ___________________

For___________________

Date___________________

Locating Address___________________

Phone No. ___________________


Figure 4: Number of Dog Bites in Guatemala City, February 1976

Weekly tabulations can occupy an inordinate amount of the time of staff members, unless care is taken to limit their proliferation. The guiding principle of reporting is to keep the number of diseases under surveillance and tabulation to an absolute minimum. Cardinal sins are, on the one hand, to not evaluate the surveillance data collected by members of the field staff and, on the other hand, to sacrifice field investigation of epidemics and disease control activities in order to keep up with tabulating the data. Arrangements should be made to whatever extent possible to delegate responsibility for tabulation to national statisticians or local individuals such as teachers, tax officers, or such volunteers as students.

The epidemiologist should also extensively use maps and graphs for visual appreciation of disease trends. This is frequently a more productive investment of the scarce time of staff members than is generating columns and figures. Maps with pins indicating the geographic clustering of cases are particularly useful for following the spread of a disease and in international relief operations in which members of the epidemiology staff may lack intimate knowledge of reporting units' proximity to each other. Well charted graphs can more sensitively indicate disease trends than numbers. This is demonstrated in Figure 4, in which reported cases of dog bites in Guatemala City following the earthquake in 1976 (37) are shown, and in Figure 5, in which reports of gastroenteritis in the disaster area are charted by weekly intervals (38). There are publications available about drafting epidemiologic visual material and graphs (39-43).

In summary, the epidemiologist and his superiors in the relief effort must anticipate that organizing effective postdisaster surveillance will itself lead to increased levels of reported disease, which may be real or only apparent. Some reports of increase in levels of disease will require field investigation, but despite efforts to document trends in the field it may be impossible to ascertain whether or not changes in levels are in fact real. However, there are three simple measures which will provide independent evidence of the validity of trends of reported disease. The following should be monitored in the weekly epidemiologic tabulations: the total number of potential reporting units; the percentage of units from which reports are submitted during the period of surveillance summaries the cornerstone of surveillance feedback. Beter, such as the registration of refugees or the opening of clinics in new areas.


Figure 5: Example of Simplified Method of Surveillance of Epidemics in Zones of Disaster: Number of Reported Cases of Enteritis by Half-Week, Locality of Zaragoza, Guatemala, March 1-December 10, 1976

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