How can we track bacterial diseases

Epidemiology

evaluates occurance, determinants, and control of health and disease in a defined human population

John Snow

Father of epidemiology; investigated 1854 london cholera outbreak; linked disease to contaminated water.

sporadic disease

occurs occasionally or at irregular intervals in human population

endemic disease

maintains a steady, low-level frequency at a moderately regular interval

Hyperendemic Diseases

gradually increase in frequency above endemic level but not to epidemic levels

outbreak

sudden, unexpected occurance of disease; in a limited segment of population

epidemic

outbreak affecting many people at once; index case; resevoir host

reservoir host

organism remains healthy while virus thrives

index case

first person identified with the disease in an epidemic

pandemic

increase in disease occurence within a large population over at least 2 countries around the world.

public health surveillance

proactive evaluation of genetic background, environmental conditions, human behaviors and lifestyle choices, emerging infectious agents and microbial responses to chemotherapeutic agents to monitor the health of a population.

information loop

public → healthcare providers → health agencies → analysis

information that is reported to health agencies

population morbidity and mortality; disease effect on school attendance; impact on employee absenteeism; animal and vector control policies

To determine if an outbreak, epidemic or pandemic is occurring, epidemiologists measure

disease frequency at single time points and over time.

morbidity rates reflects a ______. Morbidity rates characterize __ or _.

change in health status over time; incidence; prevalence

Prevalence

number of individuals infected at a specific point in time (does not distinguish new and old cases); would influenced by death, recovery, new cases.

incidence

number of new cases of disease in a period of time

Prevalence equation

((total number of cases in population)/(total population))*100

Morbidity rate/ Incidence rate equation

(number of new cases of a disease during a specified period)/(number of individuals in the population)

Mortality rate equation

(Number of deaths due to a given disease)/(size of total population with the same disease)

Communicable diseases

can be transmitted from person to person; not all infectious diseases

two types of epidemics

common source epidemic and propagated epidemic

Common source epidemic (noncommunicable)

reach a peak in a short period, result of a single, common contaminated source

Propagated epidemic (communicable)

slow and prolonged rise, results from the introduction of single infected individual into a susceptible population

The epidemic peak coincides with the _ _.

threshold density

time 0

all individuals are susceptible

day 15

epidemic peak

herd immunity

threshold percentage of the population having immunity so when isolated cases reemerge, there is no escalation of the disease through the population.

basic reproduction number (R₀)

number of susceptible individuals that can be infected from one sick person. Capacity of an infectious agents to spread. Varies depending on environment and behavior; assumes all members are susceptible; helps determine percentage of population that must be immune to achieve herd immunity.

Effective reproduction rate (R_e)

effective reproduction rate with vaccine in population

reasons for increases in emerging and reemerging infectious diseases include:

world population growth and urbanization; increases exposures to microbes or reservoirs; increased international travel; mass migrations of people; climate change

nonhealthcare acquired infections (HAI)

nosocomal infections- infections acquired by patients in hospital/clinical care facility; 5-10% of all hospitalized patients acquire HAI; often caused by opportunistic bacteria; many hospital strains are antibiotic-resistant

Fist step to prevent/ control an epidemic is to

detect the pathogen

two types of control measures

reduce/ eliminate source or reservoir of information; Reduce number of susceptible individuals and raise the general level of herd immunity

reduce/ eliminate source or reservoir of infection

social distancing and isolation of carriers, destruction of animal reservoirs, treatment of water and sewage to reduce contamination

reduce number of susceptible individuals and raise the general level of herd immunity

immunizations and prophylactic treatment to prevent infection

immunization

occurs when host’s immunity system has responded to the vaccine; vaccines attempt to induce antibodies and activated T cells to protect host from future infection

vaccinomics

integration of genomics, bioinformatics and personalized medicine; goal is to identify pathways that determine immune responses and provide innovative approaches to vaccine development

Adjuvants

mixed with antigens in vaccines to promote more efficient immune response; nontoxic material that assists in the processing of antigens by antigen-presenting cells

several types of adjuvants available

oil in water emulsions, aluminum hydroxide, beeswax, combinations of bacteria

whole pathogen vaccines

vaccines consisting of whole microbes- inactivated vaccines; attenuated vaccines; can have serious adverse reactions especially in immunocompromised individuals

inactivated vaccines (killed)

effective but less immunogenic; often requires boosters

attenuated vaccines (live but avirulent)

effective at stimulating both humoral and cell-mediated immunity; single dose

acellular or subunit vaccines

use of purified macromolecules derived from pathogenic microorganisms- avoids some some of the risks of whole cell vaccines

forms of subunit vaccines

capsular polysaccharides; recombinant surface antigens; inactivated exotoxins (toxoids)

recombinant-vector vaccines

pathogen genes that encode major antigens inserted into nonvirulent viruses or bacteria which serve as vectors and express the gene product

DNA/RNA vaccines

DNA fragments introduced into host cell; DNA taken into nucleus and pathogen’s DNA fragment is expressed; Host immune system responds to foreign proteins produced.

hurdles overcome in mRNA research

minimized RNA degradation; limited innate immunogenicity; designed a delivery system that would facilitate entry into the cell.