Tropical disease
Subtopic:
Introduction to Communicable Diseases
Communicable diseases, also known as infectious or transmissible diseases, represent a significant public health challenge, particularly in Africa where they disproportionately affect infants and children. These illnesses are caused by infectious agents and can spread directly or indirectly between people, animals, or from contaminated environments (surfaces, food, water). Alongside malnutrition, communicable diseases are major contributors to morbidity and mortality on the continent. Crucially, many of these diseases are preventable through appropriate interventions.
Communicable diseases are particularly serious in childhood due to higher exposure rates and incompletely developed immune systems. Tropical countries, including Uganda, continue to grapple with a significant burden of poverty-related communicable diseases such as diarrhea, parasitic infestations, respiratory infections, vaccine-preventable childhood illnesses, eye infections, and malnutrition. Simultaneously, these regions are experiencing a rise in non-communicable diseases like diabetes, stroke (CVA), rheumatic conditions, and cancer, creating a double burden of disease.
Communicable diseases can be broadly categorized by their mode of transmission:
Contact Contagious Diseases: Spread through direct physical contact.
Sexually Transmitted Infections (STIs) and HIV/AIDS: Transmitted through sexual contact.
Vector-borne Diseases: Spread through insects or other animals.
Waterborne and Foodborne Diseases: Spread through contaminated water or food.
Airborne Diseases: Spread through the air.
Bloodborne Diseases: Spread through contact with infected blood.
Zoonotic Diseases: Transmitted from animals to humans.
Helminthic Diseases: Caused by parasitic worms.
Causative Organisms:
African swine fever virus
Arboviruses
Bacillus anthracis
Brucella species
Dracunculus medinensis
Human immunodeficiency virus (HIV)
Influenza A virus
Measles virus
Mumps virus
Plasmodium species
Poliovirus
Rabies virus
Rotavirus
Salmonella enterica serovar Typhi
Schistosoma species
Severe acute respiratory syndrome coronavirus (SARS-CoV)
Shigella species
Trypanosoma species
Varicella-zoster virus
Vibrio cholerae
Wuchereria bancrofti
Yellow fever virus
Diseases/Infections:
African swine fever
Anthrax
Arboviral diseases
Avian influenza (Bird flu)
Brucellosis
Chickenpox
Cholera
Diarrhea (caused by rotavirus)
Dysentery
Elephantiasis
Guinea worm disease
HIV/AIDS
Malaria
Measles
Mumps
Poliomyelitis
Rabies
Schistosomiasis
Severe acute respiratory syndrome (SARS)
Sleeping sickness (African trypanosomiasis)
Trypanosomiasis
Typhoid fever
Yellow fever
The Importance of Communicable Diseases in Africa
Communicable diseases pose a significant and multifaceted threat to public health in Africa. Their importance stems from several key factors:
High Prevalence: Many communicable diseases are highly prevalent across the continent, affecting a large proportion of the population.
Severe Health Consequences: Numerous communicable diseases are serious, leading to significant morbidity (illness), disability, and tragically, high mortality rates, particularly among vulnerable populations.
Potential for Epidemics: The rapid spread of some communicable diseases can lead to widespread outbreaks or epidemics, overwhelming healthcare systems and disrupting communities.
Preventability: Crucially, many of these diseases can be prevented through relatively simple and cost-effective public health interventions. This highlights the potential for significant impact through targeted efforts.
Disproportionate Impact on Infants and Children: Infants and young children are particularly susceptible to and severely affected by many communicable diseases due to their developing immune systems, making these diseases a leading cause of childhood illness and death.
Understanding the Agents of Disease
Communicable diseases are caused by a diverse range of living organisms and agents, varying significantly in size and complexity:
Metazoa (Multicellular Organisms): These are the largest disease-causing organisms, visible to the naked eye. Examples include parasitic worms like tapeworms and filarial worms. They are complex organisms composed of many cells.
Protozoa (Single-celled Eukaryotes): These are more complex than bacteria but still single-celled. They are microscopic and include organisms like malaria parasites (Plasmodium species) and amoeba.
Bacteria (Single-celled Prokaryotes): Bacteria are simple, single-celled organisms. They are microscopic and often require staining with dyes to be clearly visible under a microscope.
Rickettsiae and Chlamydiae: These are smaller than bacteria and have the unique characteristic of being obligate intracellular parasites, meaning they can only multiply within the cells of a host organism.
Viruses: Viruses are the smallest of all disease-causing agents. They are so small they cannot be seen with an ordinary light microscope and require electron microscopy for visualization. They are also obligate intracellular parasites.
The Epidemiological Triad: Understanding Disease Patterns
The patterns of communicable diseases – why they are common in certain places and times – can be understood through the concept of the Epidemiological Triad. This model considers the interplay of three key factors:
The Agent: This is the living organism (like bacteria, virus, parasite) that causes the disease. The agent needs specific conditions to survive, grow, and multiply.
The Host: This is the person or animal that is susceptible to the disease. Factors like age, immune status, nutritional status, and pre-existing conditions influence a host’s susceptibility.
The Environment: This encompasses all the external factors that influence the agent and the host. This includes physical factors like climate and geography, biological factors like the presence of vectors (e.g., mosquitoes), and socioeconomic factors like sanitation, access to clean water, and housing.
For a communicable disease to occur and spread, the agent needs a suitable environment to thrive and a pathway to infect a susceptible host. If any part of this balance is disrupted, the chain of transmission can be broken, preventing the disease from spreading. Understanding this dynamic interplay is crucial for developing effective strategies to prevent and control communicable disease
Common Terms Used in Communicable Diseases:
Epidemic: A sudden increase in disease cases in a specific area, more than expected.
Example: A large, unexpected number of measles cases in a city.
Endemic: A disease that is always present in a certain population or region at a relatively stable rate.
Example: Malaria being consistently present in many parts of Africa.
Sporadic: Diseases occurring irregularly and occasionally, not consistently present.
Example: Isolated cases of botulism.
Pandemic: A disease that has spread across multiple countries or worldwide, affecting many people.
Example: COVID-19 affecting nearly every country.
Isolation: Separating infected individuals from those who are not infected to prevent spread.
Example: Keeping a person with active tuberculosis away from others.
Period of Isolation: The time an infected person can transmit the disease to others.
Example: The isolation period for someone with flu might be until they are no longer feverish.
Carriers: People who have the disease-causing organism but don’t show symptoms and can still spread it.
Example: Someone carrying the bacteria for typhoid fever without being sick themselves.
Incubation Period: The time between getting infected and the first symptoms appearing.
Example: The time between getting infected with chickenpox and the rash appearing.
Quarantine: Separating individuals who have been exposed to a contagious disease (but may not be sick yet) to see if they develop the illness.
Example: People exposed to measles being kept apart to monitor for symptoms.
Notifiable Diseases: Diseases that healthcare providers are legally required to report to health authorities.
Example: Cholera or polio cases that must be reported.
Pathology: The study of the nature and causes of diseases, looking at changes in tissues and organs.
African/Global Context: Strong pathology services are vital in Africa for accurate diagnosis of diseases like HIV and tuberculosis.
Aetiology: The study of the causes of diseases.
Example: Investigating what causes a new infectious disease outbreak.
Incidence: The number of new cases of a disease in a population over a specific time.
Example: The number of new HIV infections in a country this year.
Epidemiology: The study of how often diseases occur, where they are, and how they spread.
Example: Investigating why a food poisoning outbreak happened in a specific restaurant.
Virulence: The ability of an organism to cause severe disease.
Example: A highly virulent strain of influenza causes more serious illness than a less virulent one
The Transmission Cycle
Communicable diseases spread through different transmission cycles.
The transmission cycle of a disease is simply how the pathogen (the cause of the disease) moves from someone infected to someone else.
Knowing this helps us understand and prevent the spread of these diseases.
Elements of the Transmission Cycle:
Pathogen: This is the actual germ that causes the disease. Think of it as the enemy invader. It could be a virus (like the flu), bacteria (like strep throat), a parasite (like malaria), or a fungus (like athlete’s foot). Each pathogen has its own way of making people sick.
Infected Host: This is the person or animal that is carrying the pathogen. They are the source of the germ. It could be someone who is feeling sick or even someone who is carrying the germ without showing any symptoms (a carrier).
Exit: This describes how the pathogen leaves the infected host. The germ needs a way out to infect someone else. Common exit routes include:
Respiratory droplets: When an infected person coughs, sneezes, or even talks, they release tiny droplets containing the pathogen.
Fecal-oral route: The pathogen is present in the infected person’s feces and can spread if hygiene is poor, contaminating food or water that someone else ingests.
Bloodborne: The pathogen is in the infected person’s blood and can spread through direct contact with blood or shared needles.
Skin shedding: Some pathogens can be present on the skin and can spread through direct skin-to-skin contact.
Transmission: This is the process of the pathogen moving from the infected host to a new person. Think of it as the germ’s journey. Key ways this happens include:
Direct contact: Touching an infected person (like shaking hands) or their body fluids (like saliva).
Indirect contact: Touching objects or surfaces that have been contaminated with the pathogen (like doorknobs or used tissues).
Airborne: Breathing in tiny droplets or particles carrying the pathogen that are floating in the air.
Vector-borne: Being bitten by an insect or animal (a “vector”) that is carrying the pathogen (like a mosquito carrying malaria).
Environment: This is the world around us where the pathogen might be able to survive for a while outside of a host. Some germs can live on surfaces, in water, or in the soil.
Entry: This describes how the pathogen gets into a new, susceptible person. It’s the way the germ invades a new host. Common entry points are:
Respiratory tract: Breathing in air that contains the pathogen (through the nose or mouth).
Gastrointestinal tract: Swallowing food or water that is contaminated with the pathogen.
Skin: The pathogen entering through cuts, scrapes, or wounds in the skin.
Mucous membranes: The pathogen entering through the moist linings of the eyes, nose, or mouth.
Susceptible Host: This is a person who is at risk of getting infected if the pathogen enters their body. They are vulnerable to the germ. Factors that make someone susceptible include:
Lack of immunity: They haven’t had the disease before or haven’t been vaccinated, so their body doesn’t know how to fight off the pathogen.
Compromised immune system: Their body’s defense system is weakened due to illness or other factors, making it harder to fight off the infection.
Behavioral factors: Certain behaviors, like not washing hands or sharing needles, can increase the chances of exposure to a pathogen.
There are three parts of a transmission cycle for an agent or organism:
Source —-> Transmission —-> Susceptible Host
Communicable Diseases: Source, Transmission, Susceptibility & Control
Source of Infection:
An infected person, animal, or the environment (e.g., soil).
Individuals and animals can have:
Clinical disease: Showing overt symptoms.
Subclinical disease: Infected but without apparent symptoms.
Carrier state: Harboring the pathogen and potentially transmitting it without showing symptoms.
Transmission Routes:
Direct Contact:
Skin-to-skin contact
Mucous membrane contact
Sexual intercourse
Vector Transmission: Through an intermediary organism (e.g., mosquitoes).
Fecal-Oral: Ingestion of contaminated soil, food, or water.
Animal Contact: Bites or contact with animal products.
Airborne: Inhalation of infectious particles.
Vertical Transmission: From mother to child (transplacental).
Bloodborne: Contact with infected blood (e.g., injections, surgery, transfusions).
Susceptible Host:
A host with reduced resistance to a specific infection due to:
Lack of Prior Exposure & Immunity: Never encountered the pathogen before (e.g., a young child losing maternal antibodies to measles).
Compromised Immunity: Having an underlying illness (e.g., AIDS increasing risk of tuberculosis).
Malnutrition: Weakening the immune system and exacerbating infections.
Principles of Communicable Disease Control and Prevention:
The goal is to disrupt the chain of infection, shifting the balance against the pathogen. This involves:
Targeting the Source:
Treatment of infected individuals.
Isolation of infected individuals.
Reservoir control (e.g., controlling animal populations carrying disease).
Notification of cases to public health authorities.
Interrupting Transmission:
Environmental sanitation (e.g., safe water and food).
Personal hygiene practices (e.g., handwashing).
Vector control measures.
Disinfection and sterilization of surfaces and equipment.
Protecting the Host:
Immunization to build immunity.
Chemoprophylaxis (preventative medication).
Personal protective measures (e.g., masks).
Promoting better nutrition to strengthen the immune system.
Nursing Care of Patients with Infectious Diseases:
Aims of Management:
Promote Recovery: Provide supportive care to facilitate healing and prevent complications.
Prevent Transmission: Implement rigorous infection control measures.
Maintain Quality of Life: Address physical, emotional, and social needs of the patient and family.
Initial Management:
Reception: Create a welcoming and supportive environment to reduce anxiety.
Admission: Isolate patients appropriately to prevent further spread.
Positioning: Ensure patient comfort based on age and condition.
Observations: Regularly monitor vital signs and relevant indicators.
Rest: Encourage adequate bed rest to promote recovery.
Isolation and Barrier Nursing:
Isolation: Confining the patient to a designated area to minimize contact.
Barrier Nursing: Protecting healthcare workers and others through:
Gloves: For handling bodily fluids and contaminated materials.
Aprons/Gowns: To protect clothing and skin from contamination.
Masks: To prevent inhalation of airborne pathogens.
Disinfection: Cleaning surfaces with appropriate disinfectants.
Sterilization: Eliminating microorganisms from instruments and supplies.
Diet and Nutritional Support:
Fluids: Essential for hydration, temperature regulation, toxin dilution, and excretion.
Nutrient-Rich Diet:
Vitamin C (Fruit Juice): Supports appetite and immune function.
Proteins: For tissue repair and replacement.
Carbohydrates & Fats: Provide energy and warmth.
Diet Progression: Gradually increase food intake as tolerated.
Skin and Pressure Sore Care:
Daily Hygiene: Regular bed baths to maintain cleanliness and prevent skin breakdown.
Pressure Area Management: Assess and implement preventive measures for vulnerable areas (e.g., elbows, heels, sacrum).
Mouth Care:
Regular Oral Hygiene: Brushing, flossing, and mouthwash to maintain oral health and prevent infection.
Other Essential Components of Care:
Exercises: Encourage appropriate activity to maintain mobility and prevent complications.
Ongoing Observations: Continuously monitor vital signs, behavior, and response to treatment.
Accurate Records: Maintain detailed documentation of observations, interventions, and progress.
Occupational Therapy: Collaborate to help patients regain functional abilities.
Emotional Support: Provide empathy and address concerns for the patient and family.
Key Reminders:
Patient Education: Educate patients and families about the disease, transmission, and prevention.
Teamwork: Effective care requires collaboration among healthcare professionals and family.
Strict Infection Control: Maintain rigorous infection control practices to protect everyone.