Control of communicable diseases dr jamil
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Communicable diseases pose a major threat in emergency situations when populations are displaced. An outbreak will occur if the balance between the infectious agent, susceptible host population, and environment is disrupted. The document outlines key principles for controlling communicable disease outbreaks, including preventing exposure, reducing susceptibility, and managing illness. Acute respiratory infections, measles, diarrheal diseases, and malaria are the main causes of illness and death during emergencies.
Control of communicable diseases dr jamil
- 1. CONTROL OF COMMUNICABLE DISEASES Dr. Jamil Ahmad MBBS, PGDHP&M, MMPH, CDM (Japan), HRSA (Cairo)
- 2. PRINCIPLES OF COMMUNICABLE DISEASE CONTROL A communicable disease may be defined as an illness that arises from transmission of an infectious agent or its toxic product from an infected person, animal, or reservoir to a susceptible host, either directly or indirectly through an intermediate plant or animal host, vector, or environment.
- 3. Carrier A person that carries a specific infectious agent—and can transmit it to others—but has no clinical signs of infection. Case A person identified as having a specific health problem or disease of interest. Case Fatality Rate (CFR) The percentage of persons diagnosed with a specified disease who die as a result of that illness within a given period. Terms that are related to the control of communicable diseases.
- 4. Chemoprophylaxis: The administration of drugs (usually antimicrobials) to prevent the development or progression of an infection to actual disease or to stop transmission and disease in others: – Mass chemoprophylaxis — administering drugs to the entire population. – Selective chemoprophylaxis — administering drugs to the highest risk group Clinical Illness: Signs and symptoms that give evidence of an infection.
- 5. Contact: A person or animal that has had an opportunity to acquire the infection following association with an infected person or animal or contaminated environment. Drug Resistance: The ability of an infectious agent to survive despite the administration of an antimicrobial in a dose equal to or higher than the usual recommended dose. Endemic: The continuous presence of a disease or infectious agent within a geographical area.
- 6. EPI: Expanded Program on Immunization Epidemic or Outbreak: The occurrence of cases of an illness with a frequency that is clearly in excess of what is expected in a given region, therefore, demanding emergency control measures. Epidemiology: The study of the distribution and determinants of disease in time, place, and person.
- 7. Exposure: Meeting with an infectious agent in a way that may cause disease. Incidence Rate: The number of new cases diagnosed or reported with a certain disease during a defined time period (usually 1 year) divided by the total population in which the cases occurred. Incubation Period: The interval from the time of infection to the time clinical signs of illness appear. Infectious Agent: Bacteria, viruses, fungi or parasites or their products that can cause disease.
- 8. Isolation: Keeping infected persons or animals in separate places or under certain conditions for as long as they can transmit disease. This prevents or limits the direct or indirect transmission of the infectious agent to those who are susceptible to infection. Morbidity: An incidence rate which includes all persons within a given population who become ill during a specific time period. Mortality: The total number of deaths occurring in the total population during a certain period (usually 1 year) divided by the total number of people at risk. Notifiable Disease: Disease for which regular, frequent, and timely information on individual cases is considered necessary for the prevention and control of the disease.
- 9. Prevalence Rate The total number of persons having a certain disease or condition in a stated population at a particular time or period divided by the population at risk of the disease or condition at that time. Primary or Index Case A person who acquires a disease through exposure and brings it into a population. Reservoir Any person, animal, arthropod, plant soil, etc. in which the infectious agent normally lives and reproduces itself in such a manner that it can be transmitted to a susceptible host. Secondary Case A person infected by the primary case.
- 10. Surveillance Systematic collection, collation, and analysis of data and dissemination of resulting information so that action can result. Susceptible Host Person or animal not possessing sufficient resistance against a particular infectious agent to prevent contracting infection or disease when exposed to it. Transmission Any mechanism by which an infectious agent is spread from a source or reservoir to a person: – Direct transmission — immediate transfer of infectious agents to a suitable portal of entry through which infection of a human or animal may take place (direct contact or projection) – Indirect transmission — transfer of infectious agents through intermediate means: e.g., vehicle-borne (contaminated materials), vector-borne (arthropods)
- 11. Universal Precautions Simple, standard procedures to be used during the care of patients at all times to minimize the risk of transmission of blood-borne viruses, including HIV. They consist of hand washing, use of protective clothing such as gloves; safe handling of sharp instruments; safe disposal of medical waste include sharps; and decontamination of instruments and equipment. Virulence The ability of an infectious agent to invade and damage tissues of the host and/or cause death.
- 12. Basic Principles A disease epidemic or outbreak is the occurrence of cases of a particular disease in excess of the expected, therefore, demanding that emergency control measures be implemented. The threat of communicable disease outbreaks is greater after a disaster than in non-emergency situations, particularly when large populations have been displaced. However, an epidemic or outbreak will only occur if the equilibrium between the population’s susceptibility (host or reservoir), the virulence of the infectious agent (bacteria, viruses, parasites, or fungi or their products) and the environment that promotes the exposure is upset.
- 13. POPULATION •Age •Genetic susceptibility •Nutritional status •Previous exposure •Immunization status •General physical condition ENVIRONMENT •Shelter •Altitude •Humidity •Sanitation •Food supply •Water supply •Temperature •Overcrowding •Essential services AGENT •Virulence •Infectious dose •Susceptibility to drugs •Mode of transmission •Ability to adapt to change VECTOR Equilibrium Between the Population, Infectious Agent, and the Environment
- 14. Even though each emergency situation is unique, all emergencies are surrounded by the same factors, which can upset the balance between the infectious agent, the host, and the environment, as follows: Agent: Infectious disease agents are constantly searching for opportunities to multiply either in susceptible persons, vectors, animals, or in the environment. Some infectious agents cause higher rates of illness and death because they have become resistant to available treatment.
- 15. Host: Displaced persons may change the local environment or bring new or different strains of infectious agents. In addition, they may have low immunity to infections due to poor physical or nutritional status, underlying diseases, or poverty. Some individuals are more vulnerable to infectious diseases or the more severe form of the illness. For example, children less than 5 years of age (usually about 20% of the displaced population) are at greatest risk of morbidity and mortality from infectious diseases, particularly those who are malnourished.
- 16. Environment: Opportunities for infection may increase due to overcrowding, unhygienic conditions, lack of safe drinking water, etc. In addition, essential services (public health or medical) may become disrupted or overwhelmed by the emergency situation. Because communicable diseases respect no boundaries, outbreaks occurring within the displaced population may spread to the host population, and vice versa. The above risk factors may apply to either population. Whether communicable disease outbreaks occur will, therefore, depend on the type of infectious agents existing within the local environment and the refugee settlement, and the physical condition and health status of the displaced population.
- 17. Communicable Disease Cycle It is important to understand the cycle of communicable diseases. This may help to identify the individuals that are likely to transmit the disease, as well as those at greatest risk of becoming ill or dying within the population.
- 19. Control of Communicable Disease Outbreaks To improve the health of displaced populations in developing countries, disease control programs need to focus on the communicable diseases that cause the highest rates of illness and death within a community. The following approach may be appropriate for disease control programs:
- 20. 1. Preventing Communicable Disease Outbreaks The goal of prevention is to preserve the health of displaced persons by predicting and — to the extent possible — lessening the impact of any possible outbreak of disease. Preventive measures focus on the initial stages of the communicable disease cycle, namely risk and exposure factors and susceptibility to the disease, as follows: a. Prevent the development of infectious agents that can attack susceptible individuals. Since this may be difficult, minimize the multiplication of infectious agent, e.g., by chlorinating water, disposing of human faeces properly, and draining wastewater.
- 21. b. Minimize opportunities for exposure to infections — Interrupt disease transmission by treating or isolating infected persons and improving water sources and shelters. c. Reduce susceptibility to infectious diseases — Improve a population’s immunity by promoting better nutrition, immunization, and others means of self protection.
- 22. 2. Managing Communicable Disease Outbreaks Managing communicable disease outbreaks focuses on controlling the more advanced stages of the communicable disease cycle, namely the biological evidence of infection, clinical illness, and progression of disease in infected persons. Possible outbreak control measures include the following: a. Primary Prevention — preventing the development of biological and clinical signs of disease by immunizing susceptible people, chlorinating water, practicing good sanitation, etc.
- 23. b. Secondary Prevention — preventing mild illness from becoming more serious by diagnosing early and treating with antibiotics (where appropriate) and supportive care. c. Tertiary Prevention — preventing or minimizing disease complications by referring or treating individuals with cerebral malaria, tuberculosis, severe malnutrition, etc.
- 24. MAJOR DISEASE THREATS IN EMERGENCIES Displaced populations may be at increased risk of illness and death from many types of communicable diseases. Depending on the local environment, some diseases are more likely to occur in an area than others. The following table defines the diseases that are possible and likely to occur in emergency situations.
- 25. TRANSMISSION DISEASES AIR-BORNE ARI Measles Meningitis Pertussis Tuberculosis FAECAL OR FAECAL-ORAL Typhoid Cholera Diarrhoea, Dysentery Hepatitis Worms
- 26. TRANSMISSION DISEASES SEXUALLY TRANSMITTED INFECTIONS (STIs) Syphilis Gonorrhoea HIV VECTOR BORNE Malaria Dengue
- 27. Outbreaks of communicable diseases may occur among displaced populations at any time. However, the main causes of illness and death during the acute emergency phase are acute respiratory infections (ARI), measles, diarrhoeal diseases, and malaria. whereas tuberculosis, meningitis, and other diseases may become a bigger problem during the post-emergency phase.
- 28. Acute Respiratory Infections Acute respiratory infections (ARI) are the leading causes of illness in developing countries, particularly among children less than five years. Many children have 4-6 episodes of ARI per year. Death may occur when children develop pneumonia, measles, or whooping cough. About four million children die every year from pneumonia, most of them less than 2 months of age. 2 Although many disease pathogens can cause ARI, bacteria and viruses together account for 75% of all deaths from pneumonia.
- 29. The following factors may increase the likelihood of transmission and poor outcome from ARIs: – Environment — insufficient shelter, indoor air pollution (smoke from cooking fuel and cigarettes), overcrowding, and reduced access to health care. – Host — age (less than 2 years and above 65 years), low birth weight, lack of breast-feeding, malnutrition, vitamin A deficiency, incomplete immunization, and lack of maternal education. Acute respiratory infections can affect one or more parts of the respiratory system as follows: – Upper respiratory tract — nose, pharynx, epiglottis or middle ear – Lower respiratory tract — larynx, trachea, bronchi, lungs