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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 4 : Operational aspects of disease surveillance after disaster
View the documentField investigation of rumors and reports of communicable disease
View the documentGaining access to laboratories to obtain definitive diagnoses and support for epidemiologic investigations
View the documentPresenting epidemiologic information to decision makers
View the documentSurveillance during and after the recovery phase

Gaining access to laboratories to obtain definitive diagnoses and support for epidemiologic investigations

Selected issues concerning the use of laboratories in disaster situations, particularly in remote areas and in poorer countries, are discussed in this section. Details not contained here are presented in documents available elsewhere (49-51).

When the epidemiologist investigating a rumor encounters patients with symptoms compatible with the disease in question, it is imperative to collect specimens appropriate for diagnosis, and to properly handle and transport them to a competent laboratory, where they should receive priority attention. Selected laboratory investigation of symptoms or symptom complexes (such as fever-diarrhea) reported to be increasing may also be required for undertaking appropriate public health measures and developing guidelines for proper management of patients.

There are four reasons that it may be necessary to obtain laboratory confirmation of selected notifiable diseases from a sample of patients. The first of these is that not all notifiable communicable diseases can be diagnosed with confidence on the basis of clinical criteria alone. The probability of reaching a mistaken diagnosis is increased during a period of relief in which medical staff members lack experience in recognizing tropical or endemic communicable diseases. In addition, experienced physicians from the affected area may fail to consider recently introduced diseases in their differential diagnoses. In Latin America and the Caribbean, for example, influenza, dengue and typhoid fever are frequently confused in surveillance reports.

Second, the public health laboratory is essential to the promotion of efficient communicable disease control. The epidemiologist and preventive medical officer are primarily concerned with communicable diseases in general populations, rather than in individual patients. For such persons, the diagnosis of typhoid fever or measles in a hospitalized patient only represents the tip of an iceberg. Examination of the disease in family members, close contact and neighborhood populations is frequently indicated. To determine the prevalence of disease and initiate control measures, it may also be necessary to undertake community-wide surveys.

The importance of precise diagnosis of an agent causing outbreak or a prevalent communicable disease for patient management, and particularly antibiotic management, is the third reason to obtain laboratory confirmation. For example, of influenza, dengue and typhoid fever, the first two require supportive care. Typhoid fever ordinarily requires treatment with chloramphenicol or ampicillin, but not penicillin or sulfonamides. The typhoid organism has developed resistance to chloramphenicol or ampicillin in some areas, however.

The final reason why access to diagnostic laboratory facilities is important to disaster relief is that critical vaccines, antibiotics and antisera may not be immediately available or may only exist in extremely short supply. Definitive laboratory diagnosis can be of considerable help in deciding in which areas there is a real demand for such scarce resources and for planning the relief effort.

Health authorities establish priorities for processing diagnostic specimens during times of disaster. Systematic confirmation of all suspected cases of the diseases subject to international notification and/or those of selected emphasis in surveillance is of highest priority. Next to these are more common conditions (febrile diarrhea) of which there are outbreaks, which require confirmation through a sample of cases. Laboratory diagnosis of disease for the purpose of individual case management is of lower priority. Since public health and clinical directors compete for limited laboratory resources, and because emergency conditions may make it necessary for national relief authorities to utilize hospital and private laboratory facilities, it is important to pay heed to these priorities.

In Table 3 is a line-listing of the most important communicable diseases found in patients affected by disaster, and the indications for seeking laboratory diagnosis for preventive medical officers and clinicians. This is as a general guideline for emergency usage during times of disaster. As such, it presents minimal, instead of optimal, standards.

The response to be taken to suspect yellow fever exemplifies the appropriate response to one type of internationally notifiable disease. Laboratory diagnosis should be sought on all suspect cases. Viral isolation is only feasible during the first three days of illness. Acute and convalescent sera should be collected from all patients. Postmortem hepatic tissue should be obtained for histologic examination from all fatal cases. Viscerotomy, rather than autopsy, is practiced in many areas of Latin America. In contrast to suspect yellow fever is influenza, for which clinical reporting of outbreaks to the epidemiology unit is required. The unit should arrange throat washings and the obtaining of acute and convalescent sera from a small sample of acutely ill patients.

Table 3. Criteria for Collection of Specimens of Selected Communicable Diseases for Laboratory Diagnosis after Disaster (27. 49)

Disease

Class* *

Specimens for Isolation

Amebiasis

3C

Stool Blood

Chickenpox- Herpes Zoster

3C

Vesicular fluid Lesion scrapings Crusts

Cholera

1

Rectal swabs Stool Vomitus

Diarrhea Nonspecific

4

Fecal material

Diphtheria

2A

Nose/throat swabs

Ebola-Marburg Viral Disease

2A

Blood

Food Poisoning

—Staphylococcal Food poisoning

4

Samples of ingested material Fecal material

—Bacillus cereus

4


Gastroenteritis

—Epidemic Viral Gastroenteritis

4

Fecal material

—Rotavirus Gastroenteritis

4

Stool Rectal swab

Hemorrhagic Fevers of Argentinian and Bolivian Types


Blood Spleen Throat washings

Hepatitides, Viral

2A


—Viral Hepatitis A


Blood

—Viral Hepatitis B


Blood

—Viral Hepatitis Non-A, Non-B


Blood

Influenza

1 (under surveillance by WHO)
4 (other jurisdictions)

Pharyngeal/nasal swabs

Leprosy

2B

Tissue fluid from lesion Biopsy of nerve

Leptospirosis

2B

Blood Urine

Malaria

1 (under surveillance by WHO in non- endemic areas) 3C(endemic areas)

Blood

Measles

2B

Blood Conjunctivae/nasopharynx Urine

Meningitis—Meningococcal

2A

Spinal fluid Blood Nasopharyugeal swabs Petechial scrapings Ventricular/cisternal/subdural fluid

Pediculosis

5

Hair/clothing

Plague

1

Bubo fluid Portions of bubo Spleen Bone marrow Sputum Blood Ectoparasites

Poliomyelitis

1

Feces Oropharyngeal secretions

Rabies

2A

Brain Frozen skin sections Corneal impressions Mucosal scrapings

Relapsing Fever

1 (Louse-borne) 3B (Tick- borne)

Blood

Salmonellosis

2B

Fecal material Blood

Scabies

5

Scraping from lesion

Shigellosis

2B

Fecal material Rectal swabs

Streptococcal Diseases Caused by Group A (Beta Hemolytic Streptococci)

4

Blood

Tetanus

2A

Materials from wounds

Tuberculosis

2B

Sputum Gastric washings Pus Urine Spinal/pleural/synovial fluid

Typhoid Fever

2A

Blood Rectal swabs Urine specimen

Typhus Fever, Endemic Louse-borne

1

Blood

Yellow Fever

1

Blood

Whooping Cough

2B

Nasopharyngeal swabs

**
Class 1: Case Report Universally Required by International Health Regulations

This class is limited to the diseases subject to the International Health Regulations (1969) (quarantinable diseases)—cholera, plague, smallpox and yellow fever, and m the diseases under surveillance by WHO: louse-borne typhus, poliomyelitis, influenza and malaria

Obligatory case report to local health authority by telephone, telegraph, or other rapid means; in an epidemic situation, collective reports of subsequent cases in a local area on a daily or weekly basis may be requested by the next superior jurisdiction—as for example, in an influenza epidemic. The local health authority forwards the initial report to next superior jurisdiction by expeditious means if it is the first recognized case in the local area already reported; otherwise, weekly by mail or telegraphically in unusual situations

Class 2: Case Report Regularly Required Whenever the Disease Occurs

Two subclasses are recognized, based on the relative urgency for investigation of contacts and source of infection, or for starting control measures.

A. Case report to local health authority by telephone, telegraph. or other rapid means. These are forwarded to next superior jurisdiction weekly by mail, except that the first recognized case in an area or the first case outside the limits of a known affected local area is reported by telegraph; examples—typhoid fever, diphtheria.

B. Case report by most practicable means; forwarded to next superior jurisdiction as a collective report, weekly by mail; examples—brucellosis, leprosy.

Class 3: Selectively Recognized Endemic Areas

In many states and countries, diseases of this class are not reportable. Reporting may be prescribed in particular regions, states or countries by reason of undue frequency or severity. Three subclasses are recognized; A and B (below) are primarily useful under conditions of established endemicity as a means leading toward prompt control measures and to judge the effectiveness of control programs. The main purpose of O (below) is to stimulate control measures or to acquire essential epidemiological data.

A. Case report by telephone, telegraph, or other rapid means in specified areas where the disease ranks in importance with Class 2A: not reportable in many countries; examples—tularemia, scrub typhus.

B. Case report by most practicable means: forwarded to next superior jurisdiction as a collective report by snail weekly or monthly; not reportable in many countries; example—bartonellosis, coccidioidomycosis.

C. Collective report weekly by mail to local health authorites; forwarded to next superior jurisdiction by mail weekly, monthly, quarterly, or sometimes annually; examples—clonorchiasis, sandfly fever.

Class 4: Obligatory Report of Epidemics—No Case Report Required

Prompt report of outbreaks of particular public health importance by telephone. telegraph, or other rapid means; forwarded to next superior jurisdiction by telephone or telegraph. Pertinent data include number of eases, within what time, approximate population involved, and apparent mode of spread; examples—food poisoning, infectious keratoconjunctivitis.

Class 5: Official Report Not Ordinarily Justifiable

Diseases of this class are of two general kinds: those typically sporadic and uncommon, often not directly transmissible from man to man (chromoblastomycosis); or of such epidemiological nature as to offer no practical measures for control (common cold).

Diseases are often made reportable but the information gathered is put to tit> practical use. This frequently leads to deterioration in the general level of reporting, even for diseases of much importance. Better case reporting usually results when official reporting is restricted to those diseases for which control services are provided or potential control procedures are under evaluation, or epidemiological information is needed for a definite purpose.

Clinicians and epidemiologists from developed countries may feel that the guidelines in Table 3 are restrictive, but most public health officers in Latin America and the Caribbean would consider them excessive, in light of the inadequate or deteriorating state of public health diagnostic facilities throughout most of Latin America and the Caribbean. There are two reasons why such a view, even if true, is not an acceptable reason for failing to secure essential laboratory support during a period of emergency relief. First of all, the debilitated status of national public health laboratories does not necessarily provide indication of the diagnostic capability of hospital microbiology laboratories or of those in the private sector. In a major disaster, the opportunity is present to overcome normal institutional and bureaucratic barriers to the use of such facilities. The second reason for the inexcusability of failing to obtain laboratory support is that there is an international system of collaborating and reference laboratories for most diseases of public health importance that has been developed at the Pan American Health Organization and the World Health Organization. These laboratories can be called upon through national public health laboratories and PAHO/WHO to provide emergency diagnostic support. Furthermore, international relief transported by air permits the prompt shipment of specimens to reference laboratories in neighboring or industrialized countries. Annex 5 contains a list of centers and laboratories which collaborate in regard to the diseases covered in Table 3.

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