Ch. 35: Epidemiology and Public Health Microbiology

Father of Epidemiology

John Snow

• 1854 cholera outbreak in London

focus of epidemiology

Monitoring public health, responding to disease outbreaks, and investigating emerging diseases

monitoring public health

morbidity and mortality rates

respond to disease outbreaks, epidemics, and pandemics

• determine causes of outbreaks

• institute control measures

investigating emerging and reemerging diseases

• determine risk factors

• recommend control measures

sporadic disease

occasionally, irregular intervals

endemic disease

• steady low-level frequency

• common cold

hyperendemic diseases

• gradually increase

• common cold in the winter

outbreak

sudden, unexpected occurrence of disease

epidemic

• sudden increase in frequency 

• index case

pandemic

• usually worldwide

• H1N1

diseases in the US

• Public health surveillance

  • changed leading cause of death in the US

• Longer life expectancy → more sedentary lifestyle → metabolic diseases

pattern of infectious disease in a population

caused by microorganisms

communicable disease

• can be transmitted

• not all infectious diseases are communicable

types of epidemics

• common-source epidemic

• propagated epidemic

herd immunity

• Level can be altered by changes in pathogen

  • antigenic shift – small change

  • antigenic drift – large change

• if more of population is immune, there is less disease transmission

what 3 factors contribute to reemerging and emerging diseases

• animal

  • agricultural intensification

• human

  • encroachment

  • altered ecologies

  • introduction of exotic species

  • urbanization

  • population increase

  • global travel

  • biomedical manipulation

• environment

  • climate change

nosocomial infections

• aka hospital-acquired infections (HAI)

• 5 to 10% of all hospital patients

• Normal microbiota & antibiotic-resistance

  • ESKAPE

what is ESKAPE

• Enterococcus faecium

• Staphylococcus aureus

• Klebsiella pneumoniae

• Acinetobacter baumannii

• Pseudomonas aeruginosa

• Enterobacter spp.

vaccine

• whole-pathogen vaccines

• acellular or subunit vaccines

• recombinant/DNA/RNA vaccines

what leads to immunization

adjuvants

adjuvants

• nontoxic material in vax

• oil in water emulsions, aluminum hydroxide salts, beeswax

immunized hosts: who and when?

• Vaccination of children should begin at ~2 months

• Further vaccination depends on risk

  • living in close communities

  • reduced immunity

  • international travelers 

  • health-care workers 

most current vaccines active against bacteria and viruses are

whole cell vaccines

• live, attenuated vaccines

• inactivated vax

attenuated vaccines

• a single dose

• Less stable

• stimulate humoral and cell-mediated immunity

• immunosuppressed at risk attenuated may revert to virulent

• Sabin - 1960

inactivated vaccines

• are less immunogenic/pathogenic, require boosters

• More stable

• not good at stimulating cell-mediated immunity or secretory IgA

• Salk - 1955

acellular or subunit vaccines

• Use of purified molecules from microbes

• Forms of subunit vaccines

  • capsular polysaccharides

  • recombinant surface antigens

  • inactivated exotoxins (toxoids)

DNA vaccines

• DNA directly introduced into host cell 

• DNA taken into nucleus and pathogen’s DNA fragment is expressed

  • host immune system responds 

• Johnson & Johnson and AstraZeneca COVID-19 vaccine

  • adenovirus

mRNA vaccines

• Hurdles to overcome:

  • mature mRNA

  • detrimental innate immunogenicity

  • delivery of mRNA

• Can be used for 

  • bacterial, eukaryotic or viral diseases

  • cancer

bioterrorism

• “Intentional or threatened use of viruses, bacteria, fungi, or toxins from living organisms to produce death or disease in humans, animals, and plants”

  • Infect wells with ergots

  • Dip arrows in decomposing bodies

  • Infected bodies thrown over city walls

  • Use of bacterial spores

diseases considered bioterrorism

• Anthrax

• Botulism

• Smallpox

• Plague

• Cholera

• Hemorrhagic fever