Notes from PH 130 - Occupational Infections, Margaret Ryan, MD, MPH

UC San Diego Guest Presentation in PH 130 - Environmental and Occupational Health

Speaker Introduction

  • Margaret Ryan, MD, MPH

    • Specializations: Occupational Medicine and Preventive Medicine

    • Roles:

    • Clinical Professor (part-time) at Herbert Wertheim School of Public Health, UC San Diego

    • Captain, Medical Corps, US Navy (retired)

    • Medical Director of Defense Health Agency Pacific Region Immunization Program at Naval Medical Center San Diego (federal employee)

Course Objectives

Participants will be able to:

  1. Describe common occupational skin infections.

  2. Describe important occupational infections transmitted to workers from animals or the environment.

  3. Describe important occupational infections transmitted to workers from humans.

  4. Apply understanding of these hazards to address prevention of infections in the workplace.

Infection-Related Terms

  • Pathogens (Microbial Agents)

    • Definition: Microbes, germs, or bugs responsible for infections.

    • Types:

    • Bacteria

    • Viruses

    • Fungi

    • Parasites

  • Antimicrobial Agents

    • Definition: Medications and disinfectants used to treat infections and clean surfaces.

    • Categories:

    • Antibiotics (for bacteria)

    • Antivirals (for viruses)

    • Anti-fungals (for fungi)

    • Disinfectants (for surfaces and hands)

  • Immunizations

    • Definition:

    • Vaccines: induce active immune protection from a pathogen.

    • Immune globulins: provide passive immune protection by supplying antibodies.

Examples of Pathogens:

  • Bacteria: MRSA (Methicillin-Resistant Staphylococcus Aureus)

  • Viruses: Influenza

  • Fungi: Cocci

Best Practices on Naming Pathogens

  • Dr. Elizabeth King (CDC Microbiologist, 1912-1966) contributed to WHO Best Practices on naming new pathogens (published 2015).

  • Naming guidelines:

    • Names may describe:

    • Microscopic appearance

    • Clinical presentation

    • Year of discovery

    • Names should NOT use:

    • Geographic locations (e.g., Hantavirus)

    • Cultural or occupational terms (e.g., Butchers warts)

    • Animal names (e.g., swine flu)

    • People's names (e.g., Chagas disease)

Examples of Pathogen Names:

  • Lyme Disease: First identified in 1975 in a cluster of arthritis cases in Lyme, CT.

  • Legionnaires Disease: First identified in pneumonia outbreak at American Legion convention in 1976.

  • Elizabethkingia: Pneumonia-causing bacteria named in 2005 to honor microbiology pioneer.

Occupational Skin Infections

Types of Infections:

  • Bacterial Infections

  • Fungal Infections

  • Viral Infections

Bacterial Skin Infections

  • Sources:

    • Normal flora on human skin: Streptococcal and Staphylococcal bacteria

    • MRSA: Methicillin-Resistant Staphylococcus Aureus; can cause severe skin infections.

  • Infection causes:

    • Localized infections can lead to pain, swelling, redness, and ulceration.

    • More invasive infections can be life-threatening.

Visuals:

  • Microscopic images of MRSA and examples of bacterial infections at puncture wounds.

Risk Factors for Bacterial Skin Infections

  • High-risk occupations include:

    • Tool users

    • Food preparers

    • Landscapers

    • Construction workers

  • Prevention Strategies:

    • Avoid cuts and abrasions (e.g., using safety devices on tools, wearing gloves/PPE).

    • Seek prompt treatment for broken skin.

  • Implement engineering controls to prevent skin injury.

Personal Protective Equipment (PPE) for Skin Protection

  • Types of hand protection:

    • Minimal hand protection, full hand protection, partial hand protection, full body protection from cuts and abrasions (e.g., Navy SEAL trainees).

Fungal Skin Infections

  • Common fungal species:

    • Candida and Tinea species (e.g., athlete's foot).

  • Infection occurs in wet and warm skin conditions.

  • Risk occupations:

    • Dishwashers

    • Laundry workers

  • Prevention:

    • Keep skin clean and dry; gloves should not be wet inside as they can contribute to infection.

Visuals:

  • Images of fungal infections between fingers.

Viral Skin Infections

  • Paravaccinia Viruses:

    • “Orf” occurs in over 20% of sheep handlers.

    • “Milker’s nodules” were common before automated milking.

  • Risk occupations:

    • Farmers, veterinarians, zookeepers.

  • Prevention:

    • Avoiding skin contact with infected animals, wearing gloves, and washing hands.

Visuals:

  • Images of milker’s nodules.

Effectiveness of Gloves in Preventing Skin Infections

  • Study findings:

    • In a simulated setting, over 50% of healthcare workers contaminated their skin when removing gloves (Tomas ME, et al., 2015).

  • Importance of hand hygiene:

    • Handwashing or hand rubbing (before donning and after doffing gloves).

    • CDC recommends both soap and water or alcohol-based hand sanitizer.

Occupational Infections Transmitted to Workers from Animals or the Environment

Examples:

  • Histoplasmosis

  • Coccidioidomycosis (Valley Fever)

  • Hantavirus

  • Rabies

Histoplasmosis

  • Cause: Fungal spores from bird and bat droppings.

  • Pathology: Inhalation of contaminated dust can lead to lung infection (90% asymptomatic).

Risk Factors

  • Workers at risk:

    • Demolition, construction, roofing, hunting, farming.

  • Prevention Strategies:

    • Avoid exposures, wet down contaminated dust, disinfect dust, worker training, and PPE with respirators.

Coccidioidomycosis (Valley Fever)

  • Cause: Fungal spores found in dust, particularly in the San Joaquin Valley and southern US.

  • Infection rates: >60% are asymptomatic; less than 5% may develop severe disease requiring antifungal treatment.

  • Risk Occupations:

    • Demolition, construction, archeology, farming, military.

  • Prevention: Similar measures to Histoplasmosis.

Climate Change Note

  • California cases have been increasing and are expanding due to climate change.

Hantavirus

  • Transmission: Via exposure to rodent droppings.

  • Initial discovery: In southwest US (1993).

  • Complications: Rare but can include flu-like symptoms or severe Hantavirus Pulmonary Syndrome (>30% fatality rate).

  • Risk Workers: Excavation, construction, farming, park service, grounds keeping, house cleaning, pest control.

  • Prevention Strategies: Include avoiding rodent exposure, using wet cleaning, disinfecting before cleaning, and PPE with gloves and respirators.

Rabies

  • Definition: A zoonotic infection affecting both animals and humans.

  • Transmission: Through bites or scratches from infected carnivores (e.g., dogs, cats, raccoons, bats).

  • High-risk occupations include:

    • Animal handlers, wildlife workers, veterinarians.

  • Incubation: 4-8 weeks before neurological disease occurs; 100% fatal if disease progresses.

  • Prevention: Vaccination pre- or post-exposure and vaccination of domestic animals.

Vaccination in the Hierarchy of Controls

  • Hierarchy of Controls:

  1. Elimination

  2. Substitution

  3. Engineering Controls

  4. Administrative Controls

  5. Personal Protective Equipment (PPE)

  • Vaccination can effectively eliminate infection hazards by removing susceptibility among workers.

Occupational Infections Transmitted to Workers from Humans

Examples:

  • SARS-CoV-2 (COVID-19)

  • Influenza (Flu)

  • Bloodborne Pathogens

COVID-19 Overview

  • Definition: Caused by SARS-CoV-2, related to previous coronaviruses.

  • Epidemiology: Variants like delta and omicron have emerged.

  • Transmission: Infected individuals can transmit the virus several days before showing symptoms.

    • Spread via respiratory droplets and aerosols. Basic reproduction number (Ro) is >4.0.

  • Risk: Nearly all workers exposed to other people may be at risk (Gaffney et al. 2023).

  • Prevention Measures:

    • Physical distancing, mask-wearing, limiting non-essential work, vaccination primarily aimed at preventing severe illness.

Influenza (Flu) Overview

  • Infection rates: Highly infectious with classic symptoms including fever, headache, etc.

  • Statistics: Approx. 20 million cases annually in the US with 20,000 deaths.

  • Risk occupations include public service, teaching, healthcare.

  • Prevention: Include avoidance of exposure, engineering controls, administrative controls, and annual vaccination.

Special Note on Vaccine Mandates

  • Employers must offer vaccinations under OSHA’s general duty clause. Less than 50% of adults receive annual flu vaccines; mandates seen in healthcare and childcare sectors primarily for patient protection.

Highly Pathogenic Avian Influenza (HPAI)

  • Definition: A subtype of influenza viruses affecting birds, may infect other species.

  • Recent infections have risen in US poultry and dairy cows, with worker infections reported.

  • Protection protocols: Extensive PPE recommended, avoid raw milk, seasonal vaccines may help.

Bloodborne Pathogens

Types of Concern:

  • Hepatitis B Virus (HBV)

  • Hepatitis C Virus (HCV)

  • Human Immunodeficiency Virus (HIV)

Transmission and Impact:

  • Ways of transmission include breaks in skin from exposure to infected fluids.

  • Annual WHO estimates of occupational exposures result in significant new infections worldwide.

US Prevention Policies:

  • OSHA mandates prevention measures including offering vaccinations, universal precautions, engineering controls, training, and PPE requirements.

Universal Precautions Steps:

  1. Implement an exposure control plan (ECP).

  2. Annual training for employees.

  3. Awareness of common bloodborne pathogens (BBPs).

  4. Proper labeling of regulated waste and contaminated equipment.

  5. Ensure PPE usage.

  6. Proper disposal of contaminated sharps.

  7. Remove contaminated garments immediately.

  8. Handwashing after potential exposure.

OSHA's Bloodborne Pathogen Standard Success:

  • Evident in reduced numbers of occupationally acquired HIV infections from 1985-2013.

Occupational Safety and Health Act of 1970

  • Employers must ensure a work environment free from recognized hazards that may lead to death or serious harm. Compliance with safety and health standards is mandated under the Code of Federal Regulations.

Course Objectives Revisited

Participants will be able to:

  1. Describe common occupational skin infections.

  2. Describe important occupational infections transmitted to workers from animals or the environment.

  3. Describe important occupational infections transmitted to workers from humans.

  4. Apply understanding of these hazards to address prevention of infections in the workplace.

Presenter Contact Information

  • Email: m1ryan@ucsd.edu

  • Acknowledgement for participation in this class.