AH 3320: Introduction to Infectious Diseases and Healthcare Epidemiology

How is the broad field of biology defined?

The study of living organisms.

How is the discipline of microbiology defined?

The study of microbes, which are extremely small (microscopic) living organisms and certain nonliving entities.

Which two major types of microscopes are compared for viewing microorganisms?

Light microscope and electron microscope.

What is the visibility threshold for particles that can be seen by the naked human eye?

It hovers around $10\text{--}40\,\mu\text{m}$.

What particle size threshold is required for an airborne particle to be inhaled into the human respiratory tract?

$10\,\mu\text{m}$ (microns) or less.

What is the typical diameter of a human hair used for scale in microscopic comparisons?

$50\text{--}180\,\mu\text{m}$.

According to the relative size of particles scale, what is the size of fine beach sand?

$90\,\mu\text{m}$.

According to the relative size scale, what is the approximate size of a grain of salt?

$60\,\mu\text{m}$.

What is the average size of a white blood cell according to the relative size chart?

$25\,\mu\text{m}$.

What is the average size of a grain of pollen?

$15\,\mu\text{m}$.

What proportion of Americans experience allergic reactions and hay fever triggered by pollen every year?

$1\text{ in }5$ Americans.

What is the size cutoff for a particulate matter $\text{PM}_{10}$ dust particle?

$< 10\,\mu\text{m}$.

What is the approximate diameter of a red blood cell (RBC)?

$7\text{--}8\,\mu\text{m}$.

What is the typical diameter range of respiratory droplets?

$5\text{--}10\,\mu\text{m}$.

What is the diameter of a fine dust particle categorized as $\text{PM}_{2.5}$?

$2.5\,\mu\text{m}$.

What is the typical size range of a single bacterium on the relative particle scale?

$1\text{--}3\,\mu\text{m}$.

What is the size range of wildfire smoke particles?

$0.4\text{--}0.7\,\mu\text{m}$.

How long can wildfire smoke particles persist suspended in the air?

Several days, and even months.

What is the estimated size range of a coronavirus particle?

$0.1\text{--}0.5\,\mu\text{m}$.

What is the reported size of a T4 bacteriophage?

$0.225\,\mu\text{m}$.

What is the reported particle size of the Zika virus?

$0.045\,\mu\text{m}$.

In terms of scale comparison, approximately how many bacteria fit across the diameter of a single red blood cell?

$8$ bacteria per RBC.

In terms of scale comparison, approximately how many viruses fit across the diameter of a single red blood cell?

$80$ viruses per RBC.

How many meters is an Angstrom ($\text{\AA}$)?

$10^{-10}\,\text{m}$.

How many meters is one nanometer ($\text{nm}$)?

$10^{-9}\,\text{m}$.

How many meters is one micrometer ($\mu\text{m}$)?

$10^{-6}\,\text{m}$.

How many meters is one millimeter ($\text{mm}$)?

$10^{-3}\,\text{m}$.

How many meters is one centimeter ($\text{cm}$)?

$10^{-2}\,\text{m}$.

What is the reported size of a typical animal cell in nanometers?

$150,000\,\text{nm}$.

What is the reported size of a bacterial cell in nanometers?

$2000\,\text{nm}$.

What is the reported size of a Pox virus in nanometers?

$300\,\text{nm}$.

What is the reported size of a Herpes virus in nanometers?

$130\,\text{nm}$.

What is the reported size of a Foot-and-mouth disease virus in nanometers?

$24\,\text{nm}$.

What types of diseases can algae cause according to Table 1.1?

They are a very rare cause of infections, but can cause intoxications resulting from the ingestion of toxins.

Name at least five bacterial diseases listed in Table 1.1.

Anthrax, botulism, cholera, diphtheria, and tuberculosis.

According to Table 1.1, what are examples of infections caused by fungi?

Allergies, cryptococcosis, histoplasmosis, intoxications, meningitis, pneumonia, thrush, tinea (ringworm) infections, and yeast vaginitis.

According to Table 1.1, what are examples of diseases caused by protozoa?

African sleeping sickness, amebic dysentery, babesiosis, Chagas disease, cryptosporidiosis, diarrhea, giardiasis, malaria, meningoencephalitis, toxoplasmosis, and trichomoniasis.

According to Table 1.1, what are examples of viral diseases?

AIDS, 'bird flu,' certain cancers, chickenpox, chikungunya, dengue, hepatitis, influenza, measles, mumps, polio, rabies, shingles, smallpox, and Zika.

Where do Salmonella and Escherichia coli typically reside as normal flora?

In the intestinal tracts of animals and humans.

How do humans primarily become infected with Salmonella or pathogenic E. coli?

By eating contaminated food produced by animals or through contact with infected animals.

What type of microbe is Listeria?

A bacterium.

How is Salmonella characterized on the 'What is Salmonella?' informational chart?

A bacteria that can produce a diarrheal illness, typically caused by contaminated food or contact with infected animals, that runs its course in a few days.

How many illnesses does the CDC estimate Salmonella causes annually in the United States?

About $1.35\text{ million}$ illnesses.

How many hospitalizations does the CDC estimate Salmonella causes in the US each year?

$26,500$ hospitalizations.

How many deaths does the CDC estimate Salmonella causes in the US each year?

$420$ deaths.

What are the common symptoms of a Salmonella infection?

Fever, abdominal cramps, and diarrhea.

How long after infection do Salmonella symptoms typically begin?

$12\text{--}72\text{ hours}$.

How long does a typical Salmonella illness persist?

Usually lasts $4\text{--}7\text{ days}$.

Which demographic groups face higher danger from Salmonella infection?

Children younger than $5$, older adults, and sick/immunocompromised people.

Under what environmental conditions is Salmonella contamination more common?

In warmer weather and in unrefrigerated food.

What foods can harbor Salmonella bacteria?

Vegetables, eggs, chicken, pork, fruits, and even processed food.

What organism causes Cyclosporiasis, and what type of microbe is it?

Cyclospora cayetanensis; a protozoan parasite.

What fresh food items are commonly implicated in Cyclospora cayetanensis outbreaks?

Cilantro, raspberries, and basil.

What diagnostic stage of Cyclospora cayetanensis is excreted in human stool?

Unsporulated oocysts.

Where does the oocyst of Cyclospora sporulate to become infective?

In the environment.

What is the infective stage of Cyclospora cayetanensis that enters the food chain?

Sporulated oocyst.

What process occurs inside the human host after ingestion of sporulated Cyclospora oocysts?

Excystation releasing sporozoites, which invade the intestinal epithelium.

What symptoms are shared between COVID-19 and measles?

Sore throat, cough, body aches, runny nose, and fever.

What distinct physical symptoms differentiate measles from COVID-19?

Red, raised rash, and sore, watery pink eyes (inflamed eyes).

What specific symptom is highlighted as distinct to COVID-19 compared to measles?

Breathlessness.

Where does the characteristic measles rash first appear on the body?

On the forehead.

What are the small white spots inside the mouth characteristic of measles called?

Koplik's spots.

Name structural components of the measles virus virion.

Haemagglutinin, Fusion protein, Lipid bilayer, Matrix protein, Large Protein, Phosphoprotein, RNA, and Nucleocapsid.

What serious complications can result from a measles infection?

Pneumonia, severe diarrhea, encephalitis, blindness, and ear infections.

On what timeline do cold-like symptoms appear after initial measles virus infection?

$7\text{--}14\text{ days}$ after infection (around Day 7).

When do spots in the mouth appear relative to cold symptoms in measles?

$2\text{--}3\text{ days}$ after cold symptoms appear (around Day 9).

When does the measles rash appear relative to the onset of cold symptoms?

$3\text{--}5\text{ days}$ after cold symptoms appear (around Day 10).

What rare, fatal neurological condition can develop $7\text{--}10\text{ years}$ after a measles infection?

Subacute sclerosing panencephalitis (SSPE).

According to the WHO, what is the mortality rate among children who contract measles globally and in low-income countries?

About $1\text{ in }1000$ children overall, and up to $3\text{ in }100$ in low-income countries.

In what year was the first measles vaccine licensed in the United States?

$1963$.

In what year was the second dose of the measles vaccine recommended in the US?

$1989$.

In what year was measles elimination officially declared in the United States?

$2000$.

What is an opportunistic pathogen?

An organism that does not cause disease under ordinary conditions, but has the potential to cause disease should the opportunity present itself.

What are the direct mechanisms of colonization resistance displayed by commensal gut flora against pathogens?

Adhesion exclusion, carbon source limitation, micronutrient limitation, delivery of toxins, secretion of antimicrobials, and blocking virulence factors.

Give examples of commensal bacteria involved in direct colonization resistance.

Commensal Escherichia coli spp., E. coli Nissle 1917, Lactobacillus spp., and Bacteroides spp.

Between 2000 and 2021, by what percentage did global deaths from HIV/AIDS decrease?

$61\%$ decrease (dropping from $7\text{th}$ in 2000 to $21\text{st}$ in 2021).

Between 2000 and 2021, by what percentage did global deaths from diarrheal diseases decrease?

$45\%$ decrease (dropping from $6\text{th}$ in 2000 to $13\text{th}$ in 2021).

What was the leading cause of death in developing countries in 2021?

Lower respiratory infections.

What were the top four leading causes of death in developing countries in 2021?

1. Lower respiratory infections, 2. Stroke, 3. Ischaemic heart disease, 4. Malaria.

Which communicable condition was ranked 5th among leading causes of death in developing countries in 2021?

Preterm birth complications.

What rank did COVID-19 hold among leading causes of death in developing countries in 2021?

$6\text{th}$ place.

Where did diarrhoeal diseases and tuberculosis rank among leading causes of death in developing countries in 2021?

Diarrhoeal diseases ranked $7\text{th}$, and Tuberculosis ranked $8\text{th}$.

What conditions rounded out positions 9 and 10 of leading causes of death in developing countries in 2021?

Birth asphyxia and birth trauma ($9\text{th}$) and HIV/AIDS ($10\text{th}$).

According to the 2014 global death data, how many deaths were caused by respiratory infections?

$4.3\text{ million}$ deaths.

According to the 2014 infectious disease mortality data, how many deaths did diarrheal diseases cause?

$2.5\text{ million}$ deaths.

According to the 2014 global death data, how many deaths were attributed to HIV/AIDS?

$1.8\text{ million}$ deaths.

How many global deaths did Tuberculosis cause in 2014?

$1.3\text{ million}$ deaths.

How many global deaths did Malaria cause according to the 2014 data chart?

$0.8\text{ million}$ deaths.

In 2014 global data, how many deaths were caused by Meningitis?

$0.3\text{ million}$ deaths.

In 2014 data, how many deaths were attributed to Pertussis and Measles respectively?

$0.2\text{ million}$ deaths each.

How many global deaths did Hepatitis B cause in 2014?

$0.1\text{ million}$ deaths.

How many deaths were attributed to 'Other infectious diseases' in the 2014 global mortality bar chart?

$1.2\text{ million}$ deaths.

On the COVID-19 Death Simulator as of 4/1/2024, how many cumulative COVID-19 deaths and cases were recorded?

$7,008,958$ deaths and $704,539,977$ cases.

According to the COVID-19 Death Simulator, how many deaths were attributed to Coronary Heart Disease?

$37,779,024$ deaths.

According to the COVID-19 Death Simulator, how many deaths were attributed to Stroke?

$26,337,133$ deaths.

According to the COVID-19 Death Simulator, how many deaths were attributed to Influenza and Pneumonia?

$11,025,995$ deaths.

According to the COVID-19 Death Simulator, how many deaths were attributed to Tuberculosis?

$5,136,668$ deaths.

How is a communicable disease defined in epidemiology?

An infectious disease that can be transmitted from one person to another (e.g., STIs/STDs).

How is a contagious disease defined?

A communicable disease that is easily transmitted from person to person (e.g., Measles, Flu).

What is a zoonotic disease?

An infectious disease that humans acquire from animal sources/living reservoirs.