The Global Burden of Disease: Infectious Disease Epidemiology Notes

Session Objectives for Infectious Disease Epidemiology\n\n* Global Burden Description: Describe recent trends, epidemiology, and the global burden of infectious diseases.\n* Understanding Drivers: Identify and understand the drivers behind emerging and re-emerging infectious diseases.\n* Control Efforts: Recognize national and global efforts utilized to control infectious diseases.\n\n# Impact of New Administration on Infectious Disease Programs and Surveillance\n\n* Data Access and Monitoring:\n * Removal of AtlasPlus, which provided data on HIV, STIs, Tb, and Hepatitis.\n * Closure of the CDC STD testing lab responsible for drug resistance monitoring.\n* Global and National Policy Changes:\n * Halting of funding for the World Health Organization (WHO).\n * Termination of the Healthcare Infection Control Practices Advisory Committee (HICPAC), which provided critical guidance for healthcare-associated infections.\n* Surveillance and Publication Impacts:\n * Reducing foodborne surveillance to focus on only $2$ specific pathogens.\n * Delays in the publication of the Morbidity and Mortality Weekly Report (MMWR).\n * Reconstitution of the Advisory Committee on Immunization Practices (ACIP).\n\n# Global and Domestic Infectious Disease Trends\n\n* Infectious Disease Prevalence: Infectious diseases are categorized as being \"everywhere,\" involving domestic and international outbreaks.\n* CDC US-Based Outbreak Categories:\n * Domestic outbreaks related to pre-packaged foods and exotic animals.\n * International outbreaks of re-emerging and emerging infectious diseases.\n * International Health Notices include: Chikungunya, Polio, Yellow Fever, Clade II mpox, Diphtheria, Rabies, and others.\n\n# History of CDC Emergency Operations Center (EOC) Responses ($2003-2025$)\n\n* $2003-2005$: Ricin (Feb $2003$), Space Shuttle Columbia (Feb $2003$), SARS (Mar-Aug $2003$), Mpox (Jun-Aug $2003$), Hurricane Isabel (Sept $2003$), California Wildfires ($2003$), Mad Cow Disease ($2003-2004$), Avian Influenza ($2004$), West Nile Virus (Aug $2004$), Indonesia Earthquake-Tsunami ($2005$), Marburg Virus ($2005$), and Hurricanes Katrina, Rita, and Wilma (Aug-Nov $2005$).\n* $2006-2009$: Iowa Mumps ($2006$), E. Coli in spinach ($2006$), Extensively Drug Resistant Tuberculosis ($2007$), Salmonella Saint Paul in peppers ($2008$), Salmonella Typhimurium in peanut butter ($2009$), and H1N1 Influenza (Apr $2009$-Mar $2010$).\n* $2010-2015$: Haiti Earthquake and Cholera ($2010-2011$), Japan Earthquake-Tsunami Radiation ($2011$), Polio Eradication (Dec $2011$-Ongoing), MERS (Sept $2012$), Avian Influenza H7N9 ($2013$), Ebola (Jul $2014$-Mar $2016$), and Dept of Defense Anthrax Lab Sample Investigation ($2015$).\n* $2016-2025$: Zika Virus ($2016-2017$), Flint Michigan Water Contamination ($2016$), Hurricanes Harvey, Irma, Maria ($2017-2018$), Vaping-related Lung Injury ($2019$), COVID-19 (Jan $2020$-Aug $2023$), Mpox (May $2022$-Aug $2023$), Clade I Mpox (Jan $2024$-Ongoing), Dengue Oropouche (Apr $2024$-Ongoing), Influenza A/H5N1 (Apr $2024$-Ongoing), East Africa Hemorrhagic Fever (Jan $2025$-Ongoing), and Measles (Feb $2025$-Ongoing).\n\n# Challenges in the Prevention of Infectious Diseases\n\n* Decline in Routine Vaccinations:\n * Zero-Dose Children: Approximately $60 ext{ million}$ children have not received any vaccines and have aged out of routine programs.\n * Routine Coverage: Global routine vaccination coverage fell to a $13$-year low. DTP3 coverage declined by $5$ percentage points, leaving $25 ext{ million}$ children unvaccinated in $2021$.\n * Measles Surges: $47$ countries reported serious outbreaks by mid-$2023$, compared to $16$ in June $2020$.\n * Nigeria Diphtheria: Facing the largest outbreak in history with over $17,000$ suspected cases and nearly $600$ deaths.\n* Politics and Vaccine Hesitancy:\n * The percentage of young U.S. children receiving no vaccines has quadrupled since $2001$.\n * New policy shifts: Vaccines no longer universally recommended for all children include Rotavirus, Influenza, Meningococcal disease, Hepatitis A, and Hepatitis B (HBV).\n * Changes to HPV recommendations: Doses reduced from $2$ to $1$.\n * Respiratory Syncytial Virus (RSV): Newborns no longer recommended for vaccination if mothers were not previously vaccinated.\n* Measles Specifics ($2025$):\n * Investigation of a confirmed measles case in DC (June $14, 2025$) involving an international traveler at Dulles International Airport (IAD) Concourse A and baggage claim on June $8$ from $10:30 ext{ am}$ to $1 ext{ pm}$.\n* Societal Risks: Continued presence of \"chickenpox parties,\" where parents intentionally expose children to the virus.\n\n# Environmental and Climate Drivers of Disease\n\n* Climate Hazard Impacts: Climate change has exacerbated more than $100$ infections spread by vectors (mosquitoes, ticks, fleas, birds).\n* Rising Temperatures: Pose the greatest threat by increasing mosquito survival and biting rates (e.g., West Nile virus).\n* Hurricane-Related Risks:\n * Hurricane Harvey (Houston, $2017$): Potential for infectious disease sweeps after flooding.\n * Hurricane Ian (Florida): Deaths caused by Vibrio vulnificus, which causes necrotizing fasciitis (\"flesh-eating bacteria\").\n\n# Social and Economic Factors\n\n* Conflict and Displacement: Increased outbreaks in war-torn areas (Gaza, DRC) and refugee camps.\n* The Opioid Crisis Connection:\n * Vulnerability to HIV and Hepatitis C (HCV) among persons who inject drugs (PWID).\n * PWID are >16 times more likely to develop invasive MRSA infections.\n * Invasive MRSA from drug injections increased from $4.1\%$ to $9.2\%$.\n * Despite outbreaks, most substance abuse facilities do not provide testing for HIV or HCV.\n\n# Most Common Infectious Diseases ($2023-2024$)\n\n* Top U.S. Diseases (2024): Chlamydia, Influenza A and B, Staphylococcus aureus, E. Coli, Herpes simplex $1$ & $2$, Shigellosis, Syphilis, Gonorrhea, Norovirus, Salmonella, Pneumonia, Hepatitis C, HIV, and the common cold.\n* Top Global Diseases (2023 - GIDEON):\n 1. Tuberculosis (TB): $10 ext{ million}$ cases/deaths annually.\n 2. COVID-19: $770 ext{ million}$ cases, nearly $7 ext{ million}$ deaths reported by $2023$.\n 3. HIV/AIDS: $39 ext{ million}$ people living with the virus; $1.3 ext{ million}$ new infections annually.\n 4. Malaria: Half the world's population at risk; $247 ext{ million}$ cases and $\sim 620,000$ deaths in $2021$.\n 5. Influenza (Flu): Highly contagious with multiple strains.\n\n# Measures and Burden of Global Disease\n\n* Key Metrics:\n * Age Standardized Mortality Rates: Used to compare populations with different age structures.\n * Disability Adjusted Life Years (DALYs): Represents \"health gaps\"; the sum of years of life lost and years lived with disability.\n * Quality Adjusted Life Years (QALYs): Represents \"healthy years lived.\" Formula: $QALY = ext{Years of Life} imes ext{Utility Value}$.\n* Epidemiologic Transition: The gradual shift from infectious diseases to non-infectious (non-communicable) diseases as the leading cause of death over time.\n* Global Leading Causes of Death (WHO $2021$):\n 1. Ischaemic heart disease\n 2. COVID-19\n 3. Stroke\n 4. Chronic obstructive pulmonary disease (COPD)\n 5. Lower respiratory infections\n\n# Global Health Infrastructure and Priority Disease Lists\n\n* WHO Research & Development Blueprint: A strategy to prioritize pathogens for research in public health emergency contexts.\n* Priority Elements (2015): Transmissibility, severity/Case Fatality Rate (CFR), spillover potential, evolutionary potential, available countermeasures, difficulty of detection, public health context, international spread risk, and societal impact.\n* WHO 2022 Priority List: COVID-19, CCHF, Ebola, Marburg, Lassa fever, MERS, SARS, Nipah, Rift Valley fever, Zika, and Disease X (an unknown pathogen causing a potential international epidemic).\n* Notable International Organizations:\n * Gavi, the Vaccine Alliance: Improves access to vaccines for children in the world's poorest countries.\n * GOARN (Global Outbreak Alert and Response Network): Technical collaboration for rapid response to outbreaks.\n * International Health Regulations (IHR 2005): International law to prevent and respond to the spread of disease while minimizing interference with trade/travel.\n * PIP (Pandemic Influenza Preparedness) Framework: Collaborative approach for sharing influenza viruses and increasing developing country access to vaccines.\n\n# Antimicrobial Resistance (AMR) and Other Threats\n\n* Global Mortality: In $2019$, almost $5 ext{ million}$ deaths were related to AMR, a higher toll than HIV/AIDS or malaria globally.\n* U.S. Estimates: Each year, AMR causes at least $2,868,700$ infections and $35,900$ deaths. Clostridioides difficile alone causes $223,900$ cases and $12,800$ deaths.\n* Organisms of Concern: M. tuberculosis, P. falciparum, N. gonorrhoeae, and Carbapenem-resistant Enterobacteriaceae (K. pneumonia).\n* Zoonotic Burden: Zoonoses cause more than $2 ext{ billion}$ illnesses and $2 ext{ million}$ deaths per year.\n* Globalization Factor: The global aviation network allows disease to spread nearly anywhere within $24$ hours.\n\n# Progress and Response Improvement\n\n* Detection Speed: The time from outbreak start to discovery is shrinking significantly. In $1996$, the average delay was $167$ days; by $2008$, it had dropped to $20$ days.\n* Institutional Quote (IOM, 2003): \"A robust public health system… is the best defense against any microbial threat.\"