Week 11

• Subjective changes in body function that are felt by a patient as a result of disease

  • Not apparent to an observer

Objective changes in a body that can be measured or observed as a result of disease

A specific group of signs and symptoms that accompany a disease

The study of disease

The cause of a disease

The manner in which a disease develops

Invasion or colonization of the body by pathogens

• Occurs when an infection results in any change in the state of health

  • An infection may exist in the absence of a detectable disease

  • Disease may result when a particular type of microorganism locates in a part of the body where it is not normally found

• A disease that is spread from one host to another

  • Examples: COVID-19, chicken pox, measles, influenza, genital herpes, tuberculosis

Diseases that are easily and rapidly spread from one host to another

• A disease that is not spread from one host to another

  • Example: tetanus

Average time that individuals have a disease from diagnosis until they are either cured or die

Symptoms develop rapidly but has a short duration

Symptoms develop slowly, likely to last for a long period

Intermediate between acute and chronic

Causative agent is inactive for a time but then activates and produces symptoms

The presence and extensiveness of a disease in the body and its ability to cause death

No signs or symptoms

Fever, dry cough, tired, muscle pain, sore throat

Breathlessness, tachycardia, persistent cough, higher fever

Pneumonia, extreme breathlessness, chest pain, high temperature, bluish lips/face

Severe acute respiratory syndrome (SARS), inflamed alveoli, may require ventilator

Extreme inflammatory syndrome in response to severe infection

Pathogens are limited to a small area of the body

An infection spread throughout the body by the blood and lymph

Systemic infection that began as a local infection

Toxic inflammatory condition arising from the spread of microbes, especially bacteria or their toxins, from a focus of infection

Bacteria in the blood

Also known as blood poisoning; growth of bacteria in the blood; bacteria are proliferating in the blood

Toxins in the blood

Viruses in the blood

Acute infection that causes the initial illness

Opportunistic infection after a primary (predisposing) infection

No noticeable signs or symptoms (inapparent infection, asymptomatic infection)

• _____ are used to prove the cause of an infectious disease

• Exceptions to _____

  • Some pathogens can cause several disease conditions

  • Some pathogens cause disease only in humans

  • Some microbes have never been cultured

  • Several different pathogens may cause the same signs and symptoms

• Stanley Falkow - 1988

• Premise is not the ability to isolate a particular pathogen but rather to identify a gene that may cause the organism to be pathogenic

• Variables that make the body more susceptible to disease or may alter the course of a disease

  • Nutrition

  • Sex

  • Genetic inheritance

  • Climate

  • Environment

  • Vaccination

  • Age

  • Lifestyle/behaviors

  • Compromised host

Incubation period → prodromal period → period of illness → period of decline → period of convalescence

Interval between initial infection and first signs and symptoms

Short period after incubation; early, mild nonspecific symptoms

Disease is most severe

Signs and symptoms subside

Body returns to its prediseased state; recovery

Continual sources of infection

People with signs and symptoms

• May have inapparent infections or latent diseases

  • Asymptomatic carriers

  • Incubating carriers

  • Convalescent carriers

  • Chronic carriers

  • Passive carriers

Diseases primarily in wild and domestic animals that can be transmitted to humans

• Soil and water

• Foods

Requires close association between the infected and a susceptible host

Transmission from mother to fetus or newborn at birth

Spreads to a host by a nonliving object called a fomite

Transmission via airborne droplets less than 1 meter

• Transmission by an inanimate reservoir

  • Airborne

  • Waterborne

  • Foodborne

    • May involve cross‐contamination (transfer of pathogens from one food to another)

• Arthropods, especially fleas, ticks, and mosquitoes

• Transmit disease by two general methods

  • Mechanical transmission

  • Biological transmission

Arthropod carries pathogen on its feet

Pathogen reproduces in the vector; transmitted via bites or feces

• Hospitals are a major reservoir for a variety of pathogens

• Also known as nosocomial infections

• Certain normal microbiota are opportunistic and pose a risk

• Antimicrobial resistance is high among _____

Leading cause of HAIs

Individual whose resistance to infection is impaired by disease, therapy, or burns

• Direct contact transmission from hospital staff to patient or patient to patient

• Indirect contact through fomites and hospital ventilation system

  • Urinary catheters (fomite transmission)

  • Intravenous catheters

  • Respiratory aids

  • Needles

  • Surgical dressings

• Reduce number of pathogens

  • Handwashing

  • Disinfecting tubs used to bathe patients

  • Cleaning instruments scrupulously

  • Using disposable bandages and intubation equipment

• Improve patients’ resistance to infection

  • Prescribe antibiotics only when necessary

  • Avoid invasive procedures

  • Minimize use of immunosuppressive drugs

• Infection control committees in hospitals oversee and monitor infection control

Diseases that are new or changing, increasing in incidence, or showing a potential to increase in the near future

Two strains of influenza virus infect the same cell and the genomes get mixed; This makes a dramatically different virus

Random mutations can occur within the cell that a virus infects, creating small changes in virus proteins

Contributing factor of emerging infectious diseases: genetic recombination between organisms

Contributing factor of emerging infectious diseases: evolution of existing organisms

Contributing factor of emerging infectious diseases: widespread use of antibiotics and pesticides

Contributing factor of emerging infectious diseases: inherent genetic instability of some microbes

Contributing factor of emerging infectious diseases: changes in global climate and weather patterns

Contributing factor of emerging infectious diseases: modern transportation

Contributing factor of emerging infectious diseases: insect vectors transported to new areas where they become established

Contributing factor of emerging infectious diseases: ecological disaster, war, and expanding human settlement

Contributing factor of emerging infectious diseases: public health failure

The ability to cause disease

The degree of pathogenicity

• Weakening of the disease-producing ability of the pathogen

  • Attenuated vaccines contain crippled viruses or bacteria that are injected into a host to stimulate an immune response

• Mucous membranes

• Skin

• Parenteral route

  • Deposited directly into tissues when barriers are penetrated

  • Injections, bites, wounds, cuts, surgery

• Most pathogens have a preferred _____

• Infectious dose for 50% of a sample population

  • Measures virulence of a microbe

• Lethal dose for 50% of a sample population

  • Measures potency of a toxin

  • Virulence can be estimated from experimental studies

Once organisms enter a host, how do they cause disease?

• Pili

• Enzymes that harm the host or prevent detection

• Proteins that disrupt normal cellular function

• Capsule

• Enzymes that inactivate antibiotics

A genomic island that contains virulence factors

Almost all pathogens attach to host tissues in a process called _____

_____ on the pathogen bind to receptors on the host cells

_____ of Streptococcus mutans, made of dextran, enables the bacteria to adhere to teeth

_____ of Actinomyces adheres to the glycocalyx of S. mutans

_____ of SARS-CoV2 – adhere to ACE2 receptor on host cells

• Glycocalyx around the cell wall

• Impair phagocytosis

pneumonia

pneumonia and meningitis

anthrax

plague

• M protein

• Opa protein

• Waxy lipid (mycolic acid)

• Resists phagocytosis

  • Streptococcus pyogenes

• Allows attachment to host cells

  • Neisseria gonorrhoeae

• Resists digestion by phagocytes

  • Mycobacterium tuberculosis

coagulate fibrinogen forming fibrin

digest fibrin clots

digests hyaluronic acid, a host polysaccharide that hold cells together

breaks down collagen