Infection

What is an infection?

An infection is the multiplication of a parasitic organism in or on a body.

List the major categories of infectious agents.

Prions, Viruses, Eubacteria, Fungi, Protista, Animalia.

Name the kingdoms used to classify infectious agents.

Prion, Viruses, Eubacteria, Fungi, Protista, Animalia.

How do viruses generally cause disease?

Viruses cause damage by entering a host cell and replicating at its expense.

List some specific mechanisms by which viruses cause harm.

Inhibit host cell synthesis, damage plasma membrane, direct cytolysis, incite immune attack, damage antimicrobial defense cells, damage dependent cells, or cause activation/neoplastic transformation.

What is a latent viral infection?

Infected but hidden, inactive, dormant. Recrudescence can occur.

What are the components of the host's innate immune response to viral infection?

Interferon (alpha and beta) and inflammation.

What are the components of the host's adaptive immune response to viral infection?

Antibody formation (humoral immunity) and cellular immunity (mediated by T cells).

How does rapid bacterial multiplication cause disease?

It competes with the host for nutrients.

What are exotoxins? Give examples.

Substances produced by bacteria and released into the environment. Examples include diphtheria toxin, cholera toxin, tetanus, botulism.

What are endotoxins? What is their effect?

Structural components of Gram-negative bacterial cell walls that activate macrophages and stimulate the production of inflammatory cytokines.

What is the primary cellular defense against many bacteria? What does it often result in?

The neutrophil, which often results in the formation of pus.

Besides neutrophils, what other components of the immune system defend against bacteria?

Complement, macrophages, humoral (antibody), and cell-mediated immunity.

What is direct contact transmission?

Person-to-person transmission.

What is indirect contact transmission? What is a fomite?

Transmission via inanimate objects (fomites).

What are vector-borne diseases? Give an example.

Infections transmitted by the bite of infected arthropods, e.g., Zikavirus transmitted by mosquitoes.

What distinguishes droplet and aerosol (airborne) transmission?

Aerosol transmission involves particles <5um in size.

What is feco-oral transmission?

Transmission involving fecal contamination and oral intake.

What are nosocomial infections?

Hospital or ‘care’-acquired infections.

What is vertical transmission? Give an example.

Parent to offspring through genetics or pregnancy, e.g., transplacental transmission of Zikavirus.

What is horizontal transmission?

Person to person after birth.

What are zoonotic diseases?

Animal diseases spread to humans.

List strategies for preventing infection by avoiding contact.

Inherent barriers, distancing, isolation vs. quarantine, education on transmission routes, and eradication of the infectious agent.

What is passive immunity? How can it be acquired?

Transfer of antibodies or sensitized lymphocytes, providing immediate protection but no memory.

What is active immunity? What is the primary method to induce it?

Stimulation of the host's immune system to produce its own response and memory, primarily through vaccination.

What is prophylaxis in the context of infectious disease prevention?

Administration of therapeutic compounds or passive immunity before exposure to prevent disease.

List different types of vaccines.

Killed/inactivated, Toxoid, Live and Modified live, RNA vaccine, Virus vector.

What is specific treatment for infectious disease? Give examples.

Remove the cause using antimicrobial drugs, e.g., Antibiotics, antivirals, antiprotozoal.

Besides specific treatments, what other strategies are used to treat infectious diseases?

Relieving workload on affected organs, symptomatic treatment, replacing function, and passive immunity.

Define incidence.

Number of new cases of a disease each year.

Define prevalence.

Total number of occurrences of the disease in a year.

Define case fatality rate (CFR).

Percentage of the population showing signs of a disease that die of it.

Define infection fatality rate (IFR).

Percentage of the population that will die from the disease.

What terms does the WHO use to describe the status of an infection in a population?

Endemic, Epidemic, Pandemic.

What does it mean for a host to be 'infected'?

Host has the infectious agent.

What is a subclinical infection?

Infected but no clinical signs or symptoms.

What is clinical disease (or a clinical case)?

Infected and has disease.

What does 'latent' mean in the context of infection?

Infected but hidden, inactive, dormant.

What is a carrier?

Subclinical individual who transmits to others.

What is a shedder?

Individual shedding the virus or bacteria.

What is a superspreader? What is an amplifier?

A superspreader is an individual with a high viral load who emits infectious particles; an amplifier is similar.

What are some key facts about Rotavirus infection in children?

Nearly all children infected by age 4 with a high incidence leading to 100% prevalence.

What are some key features of Zikavirus?

Arbovirus transmitted by mosquitoes causing viremia, systemic inflammation, and transmission leading to microencephaly.

What is a key characteristic of Herpesviruses regarding disease mechanisms?

Capable of multiple harmful mechanisms including inhibiting host synthesis and causing direct damage.