Infectious Disease - chapt 26

Virulence

the ABILITY to cause a disease

Pathogen

an ORGANISM that causes a disease

Intrinsic Factors

What your body does

Example: a glycoprotein produced in the stomach that is necessary for the absorption of vitamin B₁₂.

Extrinsic Factors

Pathogen caused. Environmental influences, nutrition, infections, or physical trauma

Example: Exposure to toxins, temperature changes, or allergens.

Types of pathogens (3)

1. viruses

2. bacteria

3. parasites

Purpose of Vaccines

Trigger your immune response WITHOUT exposure or getting ill

Herd Immunity

If most of population is vaccinated, unvaccinated individuals will not get the disease

R₀ “R naught”

the basic reproduction number - Number that shows how contagious a disease is
R₀ = 3 then 1 infected person can get 3 people sick

Lyme Disease (Borrelia burgdorferi) discovered

Lyme, Connecticut 1970s

Lyme Disease (vectored by)

Ticks (Most common tick borne disease in US)

Lyme disease (type of bacterium)

• Spirochete (spiral shaped) and

• Gram negative (purple + lipopolysaccharide cell wall)

Lyme disease (treatment)

Antibiotics

Plasmodium

A genus of parasites that causes malaria in humans.

Plasmodium (spread)

Spread by mosquitos

Plasmodium what it does

Destroys red blood cells over time and lives inside blood or liver cells of human host.

Parasite

An organism that lives in or on another organism (the host) and gets nutrients from it. Host is harmed in the process (+/− interaction)

Parasite pro

• Have a higher reproductive rate than their hosts.

Malaria

A parasite from the genus Plasmodium (there are four main varieties that infect humans)

Malaria (vectored by)

Vectored by Anopheles mosquitoes

Malaria Global Impact (3)

1. Every year there are ~200 million new cases

2. In 2019 409,000 people died from malaria

3. 2/3rds of recorded deaths are children under 5 years old

Malaria hosts (2)

1. Human

2. Anopheles mosquito

Steps of Infection in Malaria (5)

1. Sporozoites from mosquito enter blood, infect liver

2. Merozoites release, infect RBCs

3. Gametocytes released, gametes develop in mosquito

4. Fertilization → Zygote, Meiosis -> oocyst forms

5. Sporozoites produced in mosquito

Prevention (Early Steps for Eradication)

Vector Management: Mosquito nets

Sporozoites

The infective stage of the malaria parasite

Merozoites

Motile, invasive forms of the parasite released from infected cells, primarily red blood cells, that can infect new host cells

Malaria Treatment

Antimalarial drugs exist but resistance is growing also vaccines

COVID-19

SARS-CoV-2

COVID (genetic material)

It’s an enveloped RNA virus, has:

• A lipid envelope (outer layer)

• RNA as its genetic material (not DNA)

7 coronaviruses

4 infect humans as common cold

3 can be severe:

a. SARS (Severe Acute Respiratory Syndrome – 2003)

b. MERS (Middle East Respiratory Syndrome – 2012)

c. COVID-19 (SARS-CoV-2) – began in 2019

Epidemic

Wide-spread outbreak of disease in a region

Pandemic

A disease outbreak that spreads worldwide.

COVID 19 Spread

person-to-person transmission

• Droplets (coughs/sneezes)

• Aerosols (pieces that linger in the air)

R₀ < 1

Each infection causes < 1 new case → outbreak dies out

R₀ = 1

Each case causes 1 new case → disease remains stable.

R₀ > 1

Each case causes > 1 new case → disease spreads (epidemic/pandemic)

Solutions for Reducing Spread and Impact of virus (4)

1. Herd immunity

2. Reduce R to less than 1

3. Develop Effective treatments to decrease CFR/IFR (case fatality rate)/(infection fatality rate).

4. Vaccination to stop spread