Biological Hazards & Pathogens

Lecture 7 - Biological Hazards

• Infectious diseases are host-centered
• The human body hosts many organisms
• Infectious diseases are associations that harm or bother humans; the agents responsible are pathogens
• Zoonosis is an infectious disease transmissible to people from animals

Types of Pathogens

• Worms: multicellular and parasitic
• Protozoa: unicellular and parasitic
• Bacteria: unicellular, most are not parasitic
  • Can be aerobic or anaerobic, or tolerate both
  • Some bacteria can form sores
• Viruses: consist of a strand of DNA or RNA and are parasitic (do not have cells)
• Relative size: Protozoa > Bacteria > Virus

The Body's Defense Against Pathogens

• The immune system differentiates "self" from "foreign" substances using proteins
  • Active immunity occurs when the body produces antibodies upon first exposure to an antigen to protect the host
• Vaccination does not guarantee 100% protection from a virus, but it reduces the chance of infection
  • Antigen preparation leads to active immunity
  • Antibody preparation provides passive immunity (vaccine protection)
• Herd immunity provides practical protection
  • If enough group members are immune, it becomes hard to maintain the chain of infection

Strategies for Managing Disease Transmission

• Segregation involves separating sick or exposed individuals
  • Isolation separates people with infectious illnesses
  • Quarantine separates those exposed to an infectious agent
• Sanitation practices, such as hand washing can help
• Vaccination prevents illness, even though there are not vaccines for everything
• Antibiotics treat illnesses from bacteria
  • Pathogen populations can become resistant over time
  • Methicillin-resistant Staphylococcus aureus (MRSA) quickly becomes genetically resistant due to its high reproductive rate
  • Overuse of antibiotics can lead to problems, especially when used as food additives to boost livestock
• Pesticides control vectors in disease transmission

Transmission of Infectious Diseases

• Closeness/contact leads to disease transmission
  • Droplet transmission arises from coughing and sneezing and touching sick items
    • Examples: Diphtheria, TB, pertussis, influenza, measles, mumps, rubella
  • Direct oral contact allows transmission
    • Examples: Strep, herpes simplex-1, infectious mononucleosis
  • Transmission by fomite occurs when an item or substance carries infectious organisms
    • Examples: skin cells, hair, clothing, and bedding
• Airborne transmission in aerosols (air circulation) differs from droplet transmission
  • Airborne transmission travels longer distances
• Fecal-oral transmission or diarrheal disease involves the fecal-oral pathway
  • One person's infectious diarrheal ailment becomes the next person's ailment
  • If sewage isn't controlled, waterborne transmission dominates
  • Fecal-oral transmission also occurs via soil as well as hand-to-mouth transmission
  • Cholera, typhoid fever, dysentery, giardiasis, cryptosporidium (zoonoses), hepatitis A, Norwalk virus, and polio can occur
• Non-fecal organisms are also transmitted into water or soil
  • Examples: Guinea worm disease and tetanus
• Foodborne transmissions: via food
  • Houseflies serve as mechanical vectors

Global Patterns of Infectious Disease Mortality

• Fast global spreading occurs due to travelling
• 2008 was a normal year without a pandemic
• 12.3 million deaths occurred in 2008 and led to infectious causes of death
  • 29% due to respiratory infections
  • 20% from diarrheal disease
  • 14% resulted from HIV/AIDS
• Of all global deaths in 2008, 22% occurred worldwide
  • Africa had the most at 53%
  • Southeast Asia had 27%
  • The Eastern Mediterranean had 25%

Infectious Disease as a Cause of Cancer

• Infection can elevate cancer risks
  • as seen in chronic irritation leading to cell proliferation
• Known infectious causes account for 18% of cancers
  • Liver cancer (hepatitis B and C)
  • Cervical cancer (human papilloma virus)
  • Stomach cancer (Helicobacter pylori bacterium)
• In developing countries, there is a higher percentage

Some Important Types of Pathogens

• Bacteria
  • Tuberculosis
  • Anthrax
  • Plague
• Viruses
  • Yellow Fever
  • HIV
  • Bird Flu
  • West Nile Virus
• Protozoa
  • Malaria

Tuberculosis (Bacteria)

• Is one of world's deadliest diseases
  • 1/3 of the global population is infected with TB
  • In 2011, almost 9 million people globally contracted TB
  • There were approximately 1.4 million TB-related deaths globally
  • TB is a major killer in HIV-infected individuals
  • Differences in healthcare systems worldwide create disparity
• Commonly attacks the lungs
• Symptoms involve chest pains, coughing up blood, prolonged cough for three weeks, fever, chills, night sweats, loss of appetite, fatigue, and weight loss
• Transmissions: cough, sneeze, speak, kiss, or spit from an infected person
• High-risk areas include South and West Africa and Southeast Asia

Anthrax (Bacteria)

• Bacillus anthracis is a large, spore-forming bacteria can last 100 years in soil
  • Two challenges
    • Extremely long dormancy in the soil
    • Difficulty identifying infected individuals
• Produces a toxin
• All forms can result in septicemia and death
• Bioterrorism-related agent
  • Tasteless and odorless; microscopic in size.
• Not directly transmitted between people
• Three Main Types
  • Cutaneous (on the skin)
  • Inhalation
  • Gastrointestinal
• Cutaneous
  • Most frequent naturally occurring strain (>95%)
  • Occurs following skin contact with contaminated meat, wool, or leather from infected animals
  • Incubation ranges from 1-12 days
  • Begins as small raising bump before progressing into vesicle and painless ulcer
  • Additional Symptoms: Fever, headache, and lymph gland swelling
  • Untreated, 20% results in death
• Inhalation
  • Highest mortality
  • Results from inhaling anthrax spores
  • Incubation takes 1 to 60 days
  • Initially appears as viral respiratory illness with sore throat, mild fever, muscle aches
  • Respiratory failure and shock may develop with developing meningitis
  • With supportive care, 75% results in death
• Gastrointestinal
  • From consuming of raw or undercooked meat
  • Incubation takes 1-7 days
  • Results in nausea, loss of appetite, vomiting, fever, abdominal pain, vomiting blood and bloody diarrhoea
  • Fatality ranges from 25% to 60%
  • Potential effect of early treatment is undefined

Bioterrorism

• Anthrax can be transported in mixed-in powder.
• Suspicious mails are a source.
  • Testing for contaminants or diagnosis
• Treated with antibiotics and vaccines

Plague (Bacteria)

• Caused by bacteria Yersinia pestis
• Common form
  • When a person is bitten by a flea infected by biting an infected rodent
  • Additionally, a break in the skin can cause.
  • Includes: swelling, tender lymph glands, fever, headache, chills, weakness
  • Does not spread from person to person
• Pneumonic
  • Infection in the lungs
  • Person (or animal) passes it on through the air
  • Complication of bubonic plague
• Septicemic
  • When plague bacteria multiply in the blood
  • Occurs with or without Pneumonic or Bubonic Plague
  • Like Bubonic excluding buboes
  • Does not spread from person to person.
• Bacteria is a viable bioweapon and responds to antibiotics.

Yellow Fever (Viruses)

• By mosquito bite
  • Aedes aegypti
• Three to six day of Incubation Period.
• Initial Phase
  • Includes fever, muscle pain, backache, headache, & vomiting
  • 85% will recover
• However, 15% of unfortunate victims progress to the toxic phase
  • Body becomes yellow, thus jaundice
  • Leads to internal bleeding, fatal kidney failure.
• A 50% fraction of toxic-phase victims will recover.
• In the absence of treatment, 7.5% victims expire within 10 to 14 days
• Native in West Africa, from Cameroon to Mauritania
• Areas featuring tropical/subtropical climates are more prone than temperate
• From colonization via Europe, it progressed to the Americas
• Epidemic occurred in Philadelphia in 1793 where 4,044 died
• Epidemics in Haiti in 1801 ended 90% of Napoleon's forces to stop a revolt
  • They then quarantined victims.
  • Failed to see the disease's transmission by mosquitoes

Yellow Fever after Colonization

• Many large homes in New Orleans were made with an interest in catching flowing air, so they had open verandahs/ porches/windows, giving an entry way for mosquitoes
• Yellow fever eradication occurred in North American following the mid-1900s
  • Included: vaccinations, insecticide application, and swamplands drainage
  • Disease exists in present times for nine countries from the Americas

Human Immunodeficiency Virus (HIV)

• By HIV transfer from the semen, breast milk, blood, or vaginal fluids
• Immune system weakens to life-threatening infection
• Discovered in 1981
• Now pandemic with no cure
• Highly destructive
  • 37.9 millions in 2018 with 770,000 fatalities
  • People with HIV can live over 11 years or decades without noticeable symptoms.
• However treatment will increase life expectancy
  • Though not available to everyone

Prevent HIV

• HIV prevalence peaked in 2012 and rose for two years
• If one has HIV it will lead to a secondary disease that leads to death
• Important to educate communities

Bird Flu

• From physical contact with infected birds
• Transmission by contact from human and human
• Threatens millions
• Can be prevented by cooking completely

West Nile Virus

• From insect bites

• Predominately infects birds but can be a problem in humans

• One can get fever, headaches, be weak

• Can lead to meningitis in severe cases

• Came from Egypt; first was found in US in 1999.

Prevent West Nile

• Control the mosquito exposure
• One can use tools and testing to find the dose exposure for the virus

Temperature relation in Mosquito

• Warm environments have a higher likelihood

Malaria in Mosquitos

• Protozoa Plasmodium create
• Female Mosquitos will transit malaria in humans' liver
• Can be addressed by draining and treating
• And preventing Mosquitos