This PPT gives an idea about how epidemics are a burden and what are the factors that contribute to epidemics. Preventive measures are also explained.

1. EPIDEMICS AND PREVENTION
OF INFECTIOUS DISEASES
Dr Poonam Bunwaree
MBChB, MRCP(UK)

5. A few definitions

6. • Endemic: A disease outbreak is endemic when it is consistently
present but limited to a particular region. This makes the disease
spread and rates predictable. Malaria, for example, is considered
endemic in certain countries and regions.
• Outbreak: The occurrence of more cases than expected
• Epidemic: The CDC describes an epidemic as an unexpected increase
in the number of disease cases in a specific geographical area.
• Pandemic: The WHO declares a pandemic when a disease’s growth is
exponential. A pandemic cuts across international boundaries, as
opposed to regional epidemics

7. Modes of transmission
• Airborne: transmitted by air and droplets, for example, flu, measles, SARS,
MERS;
• Blood and/or body fluids borne: transmitted through contact, including
blood transfusion, mother to child in utero, and sexual activity, for
example, Ebola virus, HIV;
• Waterborne: transmitted by water, for example, cholera;
• Zoonotic: transmitted between animals and people, by direct and indirect
contact, for example, viruses, bacteria, parasites, and fungi;
• Vector-borne: transmitted by being bitten by mosquitos, fleas, ticks etc.,
for example, malaria,dengue, plague; and
• Food-borne: transmitted by preparing and eating food, for example,
salmonella, listeria and hepatitis A.

9. Epidemics
• An unusual increase in the number of cases of a given disease in a
specific population during a particular period.
• The terms “outbreak” and “epidemic” are often used interchangeably.
• In general, an epidemic can be considered to be the simultaneous
consolidation of multiple outbreaks over a wide geographical area. It
usually involves the occurrence of a large number of new cases in a
short time—greater than the expected number.
• Examples of major epidemics include cholera and diarrhoeal diseases,
measles, malaria, and dengue fever

10. Phases of an epidemic
1. Introduction or emergence into a community.
2. Localised transmission, where sporadic infections with the
pathogen occur.
3. Amplification: The outbreak amplifies into an epidemic or
pandemic – the pathogen is able to transmit from human to human
and causes a sustained outbreak in the community, threatening to
spread beyond it.
4. Reduced transmission: when human- to-human transmission of the
pathogen decreases, owing to acquired population immunity or
effective interventions to control the disease.

11. Epidemiological link
• History of risk of infection—for example, having contact with a
person with a confirmed case of infection during its communicable
period or having been in an area of proven transmission.

12. Outbreak
• Two or more cases linked epidemiologically to one another. The
existence of a single case under surveillance in an area where the
disease did not exist is also considered an outbreak.
• An outbreak occurs when there is an unusual increase in the number
of cases of a disease beyond what would normally occur.
• The spread of the disease may be localized within a specific area (e.g.,
a community, a village, a ship, a closed institution) or the disease may
spread to several countries.
• An outbreak may last a few days, several weeks, or several years.

13. Outbreak or epidemic period
• The duration of an outbreak or an epidemic depends on the following
factors:
• The speed of the outbreak in relation to the infectivity of the agent and the
mode of transmission
• The size of the susceptible population;
• The intensity of exposure of the susceptible population;
• The incubation period of the disease;
• The effectiveness of immediate control measures.

14. Basic reproduction number
• Indicator of the contagiousness or transmissibility of infectious and
parasitic agents.

15. • Each disease has a basic reproduction number, which can be used to
calculate the speed at which a disease may spread in a population
and to understand how infectious the disease is and therefore the
level of risk associated with it.
• The epidemic spreads if and only if R0 is greater than 1 (each person
with the disease infects more than one person); if R0 is equal to 1
then there is said to be epidemic (or endemic) balance, and if R0 is
less than 1 the situation invariably leads to exhaustion of the
epidemic.

17. Epidemic curve
• Graphic representation of the daily, weekly, or monthly frequencies of the
disease on a coordinate axis, with the horizontal axis representing time and
the vertical axis representing frequencies.
• The epidemic curve usually shows a skewed distribution and has the
following features:
• A rising curve, which represents the phase when the epidemic is increasing. The
slope or steepness of the curve indicates the speed at which the epidemic is
spreading, which is related to the mode of transmission of the agent and to the size
of the susceptible population.
• A peak or plateau, which may be reached naturally or flattened through early
intervention.
• A falling curve, which represents the exhaustion phase of the epidemic; the curve’s
slope or downward trend indicates the speed at which the susceptible population is
being exhausted, whether naturally or as a result of the effect or impact of the
control measures put in place

20. Risk factors for new epidemics in the 21st
century
• New lifestyles
• Role of international travel and migration
• Overpopulated cities and crowded areas
• Potentially hazardous changes are also taking place in the use of land,
agricultural practices and food production, such as live poultry and animal
markets, and deforestation – which also leads to increased contact between
people and wildlife.
• Climate change leading to misbalances in the ecological system.
• Limited access to healthcare and poor healthcare systems
• Traditional control measures
• At times no longer efficient
• Role of antibiotic resistance

21. • Lack of equity and solidarity
• The global impact of a single pathogen may vary significantly between
settings and there is no one-size-fits-all intervention strategy.
• Access to medical countermeasures remains difficult, especially for low-
income countries and countries facing humanitarian emergencies, and this
difficulty is worsened when vaccine or treatment production is limited.
• “Infodemics” :the rapid spread of information of all kinds, including
rumours, gossip and unreliable information.
• can cause widespread public reluctance to adopt well-founded infection
control measures promoted by health authorities – and thus delay essential
interventions

23. Impact of epidemics

25. Prevention of infectious diseases

27. • Each infectious disease has specific
biological and ecological aspects,
affecting geographic regions in
different ways. Therefore, each
disease requires specific control and
preventive actions.
• However, there are effective
“universal strategies” to prevent and
mitigate infectious diseases in general,
with very robust results, especially
when such strategies consider human,
environmental, animal and pathogen
aspects in an integrated way from a
One Health perspective

28. The epidemiological triad
• The Agent - The microorganism that causes the infection and can be
in the form of bacteria, viruses, parasites or fungi
• The Host - The target of the disease
• The Environment - The surroundings and conditions (these are
external to the host)

29. Infection spread in healthcare facilities
• Elevated risk of disease transmission due to the presence and relative ratio
of susceptible individuals.
• Source:
• Environment- patient care areas, sinks, hospital equipment, countertops, medical
devices.
• People -patients, healthcare workers, or visitors.
• Transmission:
• Touch, including via medical equipment or a susceptible person (for example, MRSA
or VRE)
• Sprays or splashes (for example, Pertussis)
• Inhalation of aerosolised particles (for example, TB or Measles)
• Sharps injuries introducing blood-borne pathogens (for example, HIV, HBV, HCV)

30. Infection control within communities
• The first step when looking at infection control can start at the
community level by changing behaviour, including:
• Regular hand washing
• Appropriate use of Face-masks (protect from and prevent spread of
respiratory infections)
• Using insect repellents
• Ensuring up-to-date routine vaccinations and participating in immunisation
programmes
• Taking prescribed medications, such as antibiotics, as directed by health
professionals
• Social distancing
• Using condoms when having sex, especially with a new partner

31. Medical interventions
• Antimicrobial agents
• Antibiotic stewardship and development of new antibiotics and other antimicrobial
agents
• Vaccination
• Vaccines prevent around 2.5 million deaths each year
• After causing about 400 million deaths in the 20th century, smallpox was eradicated
in the 1970s after an international vaccination campaign coordinated by the World
Health Organization
• Large-scale immunization reduces the exposure of non-vaccinated individuals to
pathogens and interrupts or reduces the chain of disease transmission through the
process known as “herd immunity”, characterized by the presence of numerous
individuals immunized against a given pathogen.
• Anti-vaccine movement

32. • Testing and diagnosis
• The testing of infectious diseases and the identification of infected individuals among
a specific population are the most critical initiatives for the success of policies
focused on the control of infectious diseases.
• Testing is the initial step for the treatment of infected individuals.
• Second, individuals who know they are infected with a particular infectious agent can
take measures to avoid its transmission.
• Third, large-scale testing enables the identification of the populations or
communities most affected by a given infection, allowing mapping the areas where
the problem is most pronounced and directing control and prevention policies more
robustly to these target populations and specific locations.
• Four, virological surveillance trough the identification of viral strains (groups,
subtypes, or recombinant strains) estimates recent infections and provides crucial
data of viral epidemiology
• Finally, testing plays a crucial role in the surveillance of chronic infectious diseases
and controlling outbreaks and epidemics, especially using point-of-care (POC) tests

33. • Treatment
• The treatment of infectious diseases has a pivotal effect on the life quality of
infected individuals, reducing unwanted impacts of the disease on social and
economic aspects, along with the avoidance of possible co-infection-related
complications for the patient
• E.g HIV: treatment reduces the burden of the disease and also prevents the
spread of the disease

34. Reduction of contact with wildlife and
livestock
• Between 58-75% of infectious diseases that affect humans are
originated from microorganisms hosted in non-human animals.
• zoonotic origin
• The handling and consumption of meat, blood, and offal from wild animals
(bushmeat/wildmeat) are very common in different regions worldwide,
mainly in Asia and Africa, although in other regions of the world the
bushmeat consumption is also very intense.
• Bats and emergence of SARS-COV and MERS-COV
• New human infectious diseases are usually caused by pathogens that
originally circulated only in wild animals and, after a spillover event, also
infect and trigger diseases in humans
• Need to with strict sanitary rules for meat trading needs to be extended to all
meat trading locations, including popular and traditional markets

35. Biodiversity preservation and containment of
climate change
• Diverse ecosystems are more resilient to changes and insults than more
homogeneous environments
• Deforestation, mining, intensive land use, and other activities associated with the
degradation of ecosystems, increase the interaction of humans with different wild
species, facilitating spillover events. These activities also increase human
exposure to vectors of different diseases, such as mosquitoes
• The loss of vegetation cover is associated with higher levels of greenhouse gas
emissions in the atmosphere (e.g., carbon dioxide), loss of water cycle regulation,
and other environmental disturbances, fueling the rise in global average
temperature and climate changes
• Extreme climatic events, such as heavy rains, hurricanes and floods, facilitate the
proliferation of disease vectors and are associated with the increase in cases of
diseases such as gastroenteritis, leptospirosis, and cholera.

36. Vector control
• Animal vectors transmit over 17% of all infectious diseases in the world
• Vector-borne diseases are caused by viruses (e.g., Dengue virus, Zika virus),
bacteria (e.g., Rickettsial diseases, typhus), and parasites (e.g., lymphatic
filariasis, malaria, schistosomiasis).
• Mosquitoes of the genus Aedes, Anopheles and Culex, along with ticks,
triatomine bugs, aquatic snails, lice, fleas, tsetse flies, blackflies, and
sandflies are the most relevant disease vectors.
• Vector control involves a series of strategies that must be implemented
according to the needs of each location, country and epidemiological
particularities, which may involve the use of insecticides, predator species,
habitat manipulation, house improvement, the release of genetically
modified mosquitoes in the environment, among other strategies .

37. Environmental sanitation
• Adequate conditions of environmental (basic) sanitation are
determinants of population health and include mainly the access to
treated water, garbage collection, and sewage system and treatment.
• Several diseases are associated with inadequate sanitation facilities
and lack of access to treated water and sewage treatment, especially
parasitic and viral enteric diseases
• In addition to diseases transmitted by contaminated water, the lack of
sanitation facilitates the proliferation of mosquitoes that spread
numerous viral species (e.g., Dengue virus, Zika virus, West Nile virus).

38. Infectious disease surveillance
• Surveillance is one of the most effective strategies for the control of
infectious disease outbreaks and containment of emerging pathogens.
• Robust epidemiological surveillance systems allow the monitoring of the
circulation of pathogens in humans, non-human animals, and human-
animal interfaces, facilitating the early detection of emerging diseases with
potential of causing epidemics and pandemics.
• Also, epidemiological surveillance is the mechanism that allows detecting
sudden increases in cases of a particular disease.
• Currently, genome-based technologies are used in the rapid and highly
accurate diagnosis and surveillance of infections. These technologies also
allow the monitoring of outbreaks, epidemics, and pandemics accurately
and practically in real time

39. Urban planning
• Human agglomeration is an essential factor for human-to-human
transmission of infectious diseases.
• Human agglomeration, unplanned urbanization and de-urbanization
(neglected/abandoned urban areas) facilitate the emergence and
spread of infectious diseases
• associated with sustained human-to-human transmission of pathogens, lack
of sanitation, closer contact with wildlife, garbage accumulation, and
proliferation of disease vectors

40. Sex education and safe sex
• Education on STDs , treatment and PrEP

41. Access to food, food security and proper
nutrition
• The nutritional status significantly influences the susceptibility and
pathogenesis of infectious diseases in several ways.
• maternal protein deficiency was associated with increased susceptibility to
congenital Zika syndrome

42. Reduction of social inequalities
• Social inequality is one of the main drivers of poor population health.
Individuals with insufficient income are incapable of having proper
daily diets, invest in education and professional training, and have
adequate leisure activities as a way to promote physical health and
reduce stress, being, therefore, more susceptible to several diseases.

43. Prevention of infection in the healthcare
setting
•Perform hand hygiene
•Use personal protective equipment to prevent exposure to infection
•Follow respiratory hygiene/cough etiquette principles
•Ensure appropriate patient placement and isolation precautions
•Properly handle, clean, and disinfect patient care equipment and medical instruments
•Handle and sterilise textiles and laundry carefully
•Follow safe injection practices and proper handling of sharps/needles
•Ensure healthcare worker safety via IPC and post-exposure prophylaxis
•Prevention of intervention-related infections (catheter-associated urinary tract infections, intravascular
catheter-related infections, surgical site infections)
•The implementation of the specific isolation precaution when diagnosing some syndromes
•Improving the communication between health care workers especially when referring potentially contagious patients

44. • Transmission-Based Precautions used in addition to Standard
Precautions for patients with infectious disease to prevent
transmission:
• Contact precautions
• Droplet precautions
• Airborne precautions