Introduction:
During a disease outbreak, it is important to establish the disease diagnosis based on laboratory work. This helps to arrive at the cause of the disease. Anatomic pathologists play an important role in diagnosing and exclusion of infectious diseases. Many epidemics have been observed in the world due to many reasons.
What Is an Infectious Disease?
Bacteria, viruses, fungi, or parasites cause infectious diseases. Many organisms live in and on the body but may cause infection or disease under certain conditions. Infectious diseases may occur from person to person or from insects or animals. Some infections are due to consuming contaminated food or water, and others may be due to exposure to organisms in the environment.
Infectious diseases are the main reason for deaths in developed and developing countries. These diseases cause morbidity (disease or illness) and mortality (death) among immunocompromised individuals and majorly affect elderly people.
The study of infectious disease must be done under three main areas.
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Diagnosis: Reaching a diagnosis is important to control a disease and to arrive at preventive measures. This helps in understanding the disease process and exact treatment.
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Outbreak Investigations and Surveillance: During an outbreak of a disease, it becomes important to arrive at a diagnosis through laboratory work to know about the cause of the disease. The diagnosis is mainly on pathology if test results are negative or inconclusive. Pathology is important for disease surveillance and helps speed up the monitoring process. This, in turn, helps to make the process simple and efficient.
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Pathogenesis: The study of disease is done to know the pathogenesis or disease process and its progression in the host. New modern molecular techniques are employed to get information at the cellular level.
What Is the Pathology of Infectious Disease?
Individuals live in a world where there is a constant change in social, economic, and demography. Many factors are responsible for epidemics.
They are
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The mobility of people over long distances in a short period.
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Social imbalance.
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Individuals who are devoid of liberty and refugees.
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Poor vaccine coverage.
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Climate and ecosystem changes that help favor vector growth and circulation of agents.
People have been facing emerging and reemerging disease epidemics worldwide for the past 30 to 40 years. In recent years, there has been an increase in the cases of AIDS (acquired immunodeficiency syndrome), leptospirosis, dengue, and chikungunya.
Diseases like yellow fever, respiratory syncytial virus, and measles were reemerged. In recent years, there has been a resurgence of sexually transmitted diseases like HIV, syphilis, hepatitis A and B, tuberculosis, and leprosy. This scenario makes the pathology of infectious diseases important throughout the world.
The pathogenesis of infectious diseases shows the relationship between the human host, the infectious agent, and the environment. The infectious agents may be of two types. They are exogenous (not found in or on the body) and endogenous (found in the body but normally does not cause disease).
Infection may occur when exogenous agents are introduced from the outside environment or when an endogenous agent overcomes the innate immunity of the host. This may result in illness or a disease state in the host's body. The susceptibility of the host plays a major role in this regard.
The pathogenesis of infectious disease must be understood at the population level, the individual, the cell, and the gene.
Infectious disease pathology helps provide pathology relating to bacteria, fungi, mycobacteria, and parasitic infections in all tissues and organs of the body.
The techniques used for evaluation are
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Gross examination.
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Microscopic evaluation.
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Immunohistochemistry.
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Molecular evaluation - PCR (polymerase chain reaction) and in situ hybridization (ISH)
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Microbiological methods.
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Ultrastructural study.
For the past many years, pathologists have been considered to play an important role in studying the pathophysiology of infectious diseases. They were the first to study pathology. Since the outbreak of AIDS in 1980, pathologists have been confronted with an increasing number of infectious diseases for diagnosis. Pathologists looked for Many infectious diseases in the histology and cytology of samples.
Newer methods have been developed recently and used in laboratories to find the pathogen in a fixed tissue or a cytology sample. Immunocompromised individuals are increasing with higher numbers of solid organs and bone marrow transplantations, chemotherapy, and immunosuppressive medications.
Infectious diseases may be due to migrants that travel from very far places, called imported ones. These are rising in number year after year. Pathologists are confronted with newly emerging infectious diseases. Recent epidemics of viral infections show the need for pathologists to assess the cell and tissue damage caused by infectious diseases.
The advantage of the pathology of infectious disease is the possibility to associate morphologically recognized lesions with an infectious agent and its inflammatory response.
The challenging part of pathology is to develop methods to distinguish between sensitive and specific detection and identification of infectious agents in formalin-fixed paraffin-embedded (FFPE) tissue samples.
Some reasons show that the future of the pathology of infectious disease could be more bright. The reason may be decreased demand because of competition by the microbiology laboratories in detecting infectious agents. The decrease in demand has reduced the requirement for the pathology of infectious diseases.
The concept of personalized cancer medicine has increased the work of pathologists as it needs analysis of tumor tissue biopsies. Biomarker studies used in pathology laboratories (immunohistochemistry, ISH, or molecular analysis) can be used for infectious diseases. The autopsy rate has been reduced for detecting the pathology of infectious diseases.
The improvement of infectious disease pathology can be done through
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Well-chosen but limited antibodies and probes should be available in the laboratories.
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Molecular methods for identifying infectious agents have yet to be developed, as in oncopathology. Hence, polymerase chain reaction can be used.
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Workshops as training programs on pathology should be conducted.
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Quality assurance programs are to be set for comparison of different methods.
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Focussing on bringing together infectious disease physicians, microbiologists, and pathologists.
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Supporting research in infectious disease pathology and research should be increased.
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Developing telepathology to help facilitate consultation of infectious disease cases.
Conclusion:
Despite the availability of programs to fight against infectious diseases, there is a rise in infectious disease cases. Hence, it is important to provide facilities needed by pathologists to get their help in fighting against infectious diseases.
