Visualizing Human Bio Ch 10

Epidemic

a disease that affects many individuals at once, spreading rapidly via infection from one person to the next in an area where the disease is not permanently or traditionally found

Pandemic

An epidemic becomes a pandemic when a very large number of people are affected, over a very wide geographic area (usually the entire globe)

Current epidemics

HIV, flu, smallpox, polio, COVID, measles; tuberculosis, plague, and leprosy are all bacterial diseases that have reached epidemics but aren't on the 'top 5' list

Best defense against epidemics

washing hands thoroughly and often

Epidemiology

the application of the scientific method to the field of disease; epidemiologists first observe the disease process, then they hypothesize the origin of the disease and who is most susceptible

Goal of epidemiology

to stop the current epidemic and prevent its return

Disease process

Epidemics begin with a simple process: The pathogen enters the human body (aka the host), alters the physiology of the body to ensure its own survival, causing discomfort, disease, and possibly death

Mode of transmission

Entry into the host occurs through physical contact with an infected person, contact with airborne pathogenic particles, or direct injection of the pathogen into the body

Effects of pathogens

Many pathogens produce toxins that cause illness; age influences the severity of any disease

Bacteria

prokaryotic cells that can be found in the ground, water, air, and inside animals; generally much smaller than eukaryotic cells and have no internal membranes or nucleus

Bacterial classification

Bacteria are classified by shape, staining, and genetics (especially DNA); shapes include spherical (cocci) and rod-shaped (bacillus)

Gram-positive bacteria

retain an initial purple color from the gram stain

Gram-negative bacteria

lose the initial stain and pick up a red secondary stain

Antibiotics

drugs that interfere with cellular processes that bacterial cells undergo every day

Mechanisms of antibiotic resistance

Bacteria can become resistant through changes in membrane permeability, receptor proteins, pumping antibiotics out, or producing enzymes that destroy antibiotics

Preventing antibiotic resistance

Avoid buying antibacterial soap, take the full prescription of antibiotics, and do not dump old antibiotics into the water supply

The plague

A serious disease caused by the bacterium Yersina pestis, carried in fleas that live on rodents

Bubonic plague

Symptoms appear 2-5 days after being bitten; includes high fever, rapid heartbeat, swollen lymph nodes, and mental confusion

Pneumonic plague

Infects the lungs via inhalation; highly contagious and can cause death within 48 hours if untreated

Septicemic plague

Indicates that the bacterium is found in the patient's bloodstream; can result in death without symptoms appearing

Leprosy

Caused by the bacterium Mycobacterium leprae, attacks the skin and nerves, leaving serious scars and dead tissue

Treatment of leprosy

Can be completely cured using a multidrug antibiotic therapy; treatment takes 6-12 months

Tuberculosis (TB)

Historically a devastating disease

Symptoms of Tuberculosis

Symptoms include coughing up blood, weakness, weight loss, chest pains, fever, and night sweats.

Treatment of Tuberculosis

Given the proper antibiotics, TB can be effectively treated within six months.

Methicillin-Resistant Staphylococcus aureus (MRSA)

MRSA is a strain of Staphylococcus aureus that is resistant to methicillin, amoxicillin, penicillin, oxacillin, and many other common antibiotics.

Risks of MRSA

MRSA can be life-threatening if it enters the body through a cut or open wound.

History of MRSA

MRSA appeared in 1961 in isolated hospitals and is now found in many hospitals and emergency rooms.

Viruses

Viruses lack most characteristics of life: they cannot reproduce without a host cell, don't metabolize, and are not composed of cells.

Structure of a Virus

A virus is a small piece of nucleic acid (DNA or RNA) contained inside a protein coat, called a capsid.

Bacteriophages

Some viruses, called bacteriophages, attack bacteria cells.

Viral Infection Process

Viruses inject their nucleic acid into the host cell and take over its functioning, leading to the production of new viruses.

Antibiotics and Viruses

Viruses are not affected by antibiotics as they have no cell wall, metabolic pathways, or protein synthesis to disrupt.

Lysogenic Cycle

Viral DNA may remain dormant in the host cell, as happens in viruses that have a lysogenic cycle of replication.

Lytic Cycle

In the lytic cycle, viral DNA immediately affects the host cell.

Poliomyelitis (Polio)

Polio attacks the nervous system and was a serious threat to infant health.

Transmission of Polio

The virus enters through the mouth, reaches the intestine, and multiplies; it can then attack the nervous system.

Paralysis from Polio

In the worst cases, total paralysis can result after just a few hours of viral attack (1 in 100 infected individuals will develop paralysis).

Symptoms of Polio

Usual symptoms include neck pain, fever, fatigue, vomiting, and pain in the limbs.

Spread of Polio

Infected people can spread the virus for the first few weeks of infection through feces.

Endemic Countries for Polio

Poliomyelitis is currently endemic in Nigeria, India, Pakistan, and Afghanistan.

Measles

Measles is an incredibly contagious disease spread through person-to-person contact and inhaling infected droplets.

Symptoms of Measles

Symptoms begin 10-12 days after infection and include high fever, runny nose, cough, watery eyes, and characteristic white spots inside the mouth.

Complications from Measles

Children can develop life-threatening complications; pneumonia is the leading cause of death in measles cases.

Ebola

Ebola is transmitted by direct contact with blood and bodily fluids of infected people.

Symptoms of Ebola

Symptoms begin anywhere from 2-21 days after contact and include sudden fever, intense weakness, severe headaches, muscle pain, and sore throat.

Influenza

The most devastating epidemic to the human population.

Spanish flu

In 1918, the Spanish flu killed more than 40 million people.

Asian flu

A strain of influenza that caused significant numbers of deaths worldwide in 1957.

Hong Kong flu

A strain of influenza that caused significant numbers of deaths worldwide in 1968.

Influenza symptoms

Causes respiratory distress, muscle aches, fever, chills, general lethargy, and severe headaches.

Influenza A

More virulent than influenza B, responsible for pandemics of the past century.

Influenza B

The common flu, easily passed from person-to-person through droplets from coughing and sneezing.

Transmission of influenza

The infected individual can spread the flu virus from a day prior to feeling symptoms to seven days afterward.

Avian flu

A type A influenza that currently resides in domestic chicken populations in Asia.

Fungi

Eukaryotic organisms that play a major role in the decay process but generally don't cause epidemics.

Athlete's foot

An example of a fungal infection.

Yeast infections

An example of a fungal infection.

Aspergillosis

A fungal infection of the respiratory tract that can cause asthmatic symptoms.

Zygomycosis

A fungal infection of the blood vessels predominantly found in patients with a compromised immune system.

Amoeba

Protists contracted from contaminated water sources responsible for dysentery.

Dysentery

A disease that can reach epidemic proportions in areas with poor sanitation.

Malaria

A serious disease worldwide, infecting approximately 515M people per year and killing 3-4M.

Anopheles mosquito

The carrier of malaria.

Mosquito control

The best prevention for the spread of malaria.