Week 12

Introduction to Global Health

• Most deaths from infectious diseases are caused by a few pathogens.
• About two-thirds of deaths from infections are caused by around 20 common species.
• These include HIV, TB, malaria, respiratory illnesses, and diarrhea.
• COVID-19 is now included in this list after emerging as an infectious disease.

Important Paired Concepts

• Infectivity: How well a pathogen can enter and multiply within a host.
  • Capacity of an agent to enter and multiply in a susceptible host, producing infection or disease.
• Virulence: How severe the illness is in the host.
  • Refers to the severity of the disease produced, including severe clinical manifestations or fatality rates.

Important Concepts

• Index case: The first case to come to the attention of authorities during an outbreak.
• Zoonosis: An animal infection transmissible to humans.
• Spillover: The moment a pathogen passes from one species to another.
• Reservoir host: A living organism that harbors the pathogen with little or no illness.
• Amplifier host: A creature in which a parasite replicates and spreads prodigiously.

The Epidemiologic Triangle

• The epidemiologic triangle consists of:
  • Host: Who is affected.
  • Agent: What is the cause.
  • Environment: Where it occurs.
• Mission of the epidemiologist is to break one side of the triangle to disrupt disease transmission.
• Host factors include age, sex, race & ethnicity, SES, occupation, activities.
• Environment factors include rural/urban settings, specific locations, ecology.
• Agent factors include the characteristics of the pathogen

Cholera

• Bacterial illness caused by Vibrio cholerae; can be fatal within hours if untreated.
• Causes 1.3 million – 4.0 million cases & 21k – 143k deaths annually.
• Global spread in the 19th century; now endemic in many countries.
• Transmission linked to inadequate access to clean water and sanitation.
• High-risk settings include peri-urban slums and camps for internally displaced persons or refugees.

The Broad Street Pump

• John Snow investigated the 1854 Cholera outbreak.
• Snow looked for anomalies, like the work house and the brewery, to support his waterborne theory.
• The miasma theory conflicted with Snow’s findings; there was opposition to Snow’s findings.

Drawing the Ghost Map

• Uneven distribution of deaths further away from Broad St.
• Snow focused on exceptions to the rule, seeking pockets of life where death was expected and vice versa.
• He innovated an uneven circumference to show proximity to the pump by walking distance.

Reference Point

• Snow imagined an overview of the Golden Square neighborhood, with a boundary line around the Broad St pump.
• People inside the border lived closer to the poisoned well; those outside used other water sources.

Statistical Case Against the Pump

• 73/83 deaths were in houses closer to the Broad St pump than any other public water source.
• 61/73 were habitual drinkers of Broad St water.
• 6/83 were not Broad St drinkers.
• Compelling Broad St connections for 8/10 cases outside the perimeter.
• Final death toll: Nearly 700 people within 250 yards of the Broad Street pump died within 2 weeks.

Snow’s Impact

• Did NOT meaningfully curtail the 1854 cholera epidemic.
• Dissipation or disabling of V cholerae within the well.
• Snow won over Board members due to fear that he might be right.
• Pump handle removed Friday, Sept 8th, after new infection had ceased.
• Removal of the pump handle prevented re-contamination when Thomas Lewis fell sick.
• DID prevent future outbreaks.
• Shaped epidemiology as a discipline, while making contributions to environmental health & urban planning.

Epidemiologic Triangle for 1854 Cholera

• Host = who?
• Agent = what?
• Environment = where?

Influenza

• Seasonally circulating viral disease.
• CDC estimates 9M to 45M cases annually in US, with 12,000 to 61,000 deaths.
• Covid comparison (mid-March 2020 to mid-March 2021): 29M cases, 530,000 deaths.
• In the first year, Covid accounted for 8.6x as many deaths as a bad flu year & 44.2x as many deaths as a mild flu year.

Pandemic Influenza of 1918

• Infected 1/3rd of the world’s population and killed between 20 & 50 million people.
• CFR somewhere between 4-10%, as compared to the 0.09% CFR for seasonal flu.
• Spread to all continents in waves; deaths concentrated in poor countries due to malnutrition from colonization.

Pandemic Influenza of 1918

• A large portion of the dead were previously-healthy young adults.
• Biggest spike was in adults aged 20-40, especially including pregnant individuals.

W-Shaped Mortality Curve

• Mortality rates among different age groups during the 1918 pandemic

Pandemic Influenza of 1918

• Some patients had common flu symptoms: headache, fever, malaise, cough.
• Others had severe symptoms: agonizing pain in joints, extreme fever and chills.
• Some had pockets of air under the skin, due to ruptured lungs, causing crackling sounds.

Flattening the Curve

• Illustrates the impact of protective measures on managing the quantity of cases over time to not exceed healthcare system capacity.
• Without protective measures there is a steep high curve.
• With protective measures the curve is broader and flatter, staying within healthcare system capacity.

Philadelphia

• 748 Deaths per 100,000 after 24 weeks of the pandemic.
• They waited eight days after their death rate began to take off before banning gatherings and closing schools.
• Endured the highest peak death rate of all cities studied.

Other Cities in the US in 1918

• New York
  • 452 Deaths per 100,000
  • Began quarantine measures very early, 11 days before the death rate spiked.
  • The city had the lowest death rate on the Eastern Seaboard.
• St. Louis
  • 358 Deaths per 100,000
  • Had strong social distancing measures and a low total death rate.
  • The city successfully delayed its peak in deaths, but faced a sharp increase when restrictions were temporarily relaxed.

Avian Influenza: H5N1 (Hong Kong, 1997)

• 18 human cases
• 6 died = 33% CFR
• 1.6 million birds slaughtered

Avian Influenza: H5N1

• Can circulate in wild & domesticated bird flocks and can spread to other animals, including cattle.
• Human infections have historically been very rare but also very deadly.
• ~900 cases since 2003
• 50% CFR
• Overwhelmingly have occurred among poultry & dairy workers
• Small, incremental evolutionary changes could allow for greater human-to-human transmission.
• Influenza viruses can evolve rapidly when 2 or more flu varieties infect the same host simultaneously & reshuffle their genetic material.
• This is more likely when there are a diverse range of host species (Barrett 2025).

Avian Influenza: H5N1

• Stage 1: Pathogen transmission occurs only between nonhuman animals.
• Stage 2: Pathogen can also be transmitted to humans, but is not yet adapted for human-to-human transmission.
• Stage 3: Pathogen is fully capable of human-to-human transmission.
• (Ron Barrett/CC BY-SA) (Barrett 2025)

Global Surveillance for Human Infection with Avian Influenza A(H5) Viruses

• The overall objective is to detect and characterize any influenza A(H5) viruses infecting humans in order to:
  • (1) promptly trigger public health control and response actions,
  • (2) assess the trends of such infections and the public health risks posed (including the risk of a pandemic);
  • and (3) inform global pandemic preparedness activities.
• Countries are required to report a single case of human infection with a new influenza subtype that fulfils the WHO case definition within 24 hours 4/11/25.

Steps to Lessen the Risk of Avian Influenza for Humans

• Change agricultural policy to move away from large-scale housing and international transfers of live poultry.
  • Most circulation of avian influenza is in cramped factory farming conditions, not in wild birds.
• Increase vaccination against common influenza viruses in people.
  • Reduces likelihood of common human flu varieties mixing with avian flue.
• Improve nutrition & sanitation in world’s poorest populations.
  • Better nutrition increases resistance to new infections.
  • Better sanitation reduces how much and how often people are exposed to new pathogens.

The Epidemiologic Triangle for Avian Influenza Today

• Host = who?
• Agent = what?
• Environment = where?

WHO Position on Abortion

• Defines health as a state of complete physical, mental and social well-being.
• Requires that all individuals have access to quality health care, including comprehensive abortion care services.
• Lack of access to safe abortion care poses a risk to the physical, mental and social well-being of women and girls.
• Induced abortion is a simple and common health-care procedure.
• Almost half of all pregnancies are unintended; 6 out of 10 unintended pregnancies and 3 out of 10 of all pregnancies end in induced abortion.
• Abortion is safe when carried out using a WHO-recommended method and by someone with the necessary skills.
• When women face barriers to obtaining quality abortion, they often resort to unsafe abortion.

WHO Position on Abortion

• Six out of 10 unintended pregnancies end in induced abortion.
• Abortion is a common health intervention and is very safe when carried out correctly.
• However, around 45% of abortions are unsafe.
• Unsafe abortion is an important preventable cause of maternal deaths and morbidities.
• Lack of access to safe, timely, affordable and respectful abortion care is a critical public health and human rights issue.

Abortion Access and Safety

• Complications from unsafe abortion account for 13% of maternal mortality worldwide.
• Deaths from safe abortion are negligible, <1/100 000.
• In regions where unsafe abortions are common, the death rates are high, at >200/100 000 abortions.
• Physical health risks associated with unsafe abortion include:
  • incomplete abortion
  • hemorrhage
  • infection
  • uterine perforation
  • damage to the genital tract and internal organs

Abortion Access and Safety

• Abortion Rates Have Decreased in Countries Where It Is Legal

Global Abortion Policies

• On Request (Gestational Limits Vary)
• Broad Social or Economic Grounds
• To Preserve Health
• To Save a Person's Life
• Prohibited Altogether
• Varies at State Level

US Abortion Policies

• Expanded Access Protected Not Protected Hostile Illegal

Global Abortion Policies Database

• A tool to expand knowledge, encourage transparency, and promote accountability.
• WHO SRHR tool

Abortion Policy: Ireland

• In 2018, the Irish parliament legalized the termination of pregnancy before twelve weeks, as well as in cases in which the health of the mother is at stake.
• The 2012 death of Savita Halappanavar reignited public debate and protest and prompted a countrywide referendum to overturn the amendment; the referendum passed with 66 percent of the vote.
• In 2019, abortion was legalized in Northern Ireland, which is part of the United Kingdom (UK).

Abortion Policy: Honduras

• Abortion has been banned since 1985.
• Emergency contraception has been banned since 2009.
• In 2021, the abortion ban was enshrined in the country’s constitution
• UN estimates that between 50,000-80,000 unsafe abortions take place in Honduras each year.

US Relationship to Abortion Policy Globally

• US has historically been the largest funder of reproductive health globally, but not of abortion services.
• USAID – included contraception access & other reproductive health programs.
• PEPFAR – focused on HIV prevention & treatment.
• Global Gag Rule as on-again/off-again predictable policy that further distances US foreign aid from any work related to abortion.
• The US has been the only donor government to explicitly restrict funding for abortion – this reinforces stigma in addition to directly impacting programs.

Medication Abortion Protocol

• The most common medication abortion regimen in the United States involves the use of two different medications:
  • Mifepristone: AKA RU-486, “the abortion pill”
    • Mifepristone works by blocking progesterone, a hormone essential to the development of a pregnancy, and thereby preventing an existing pregnancy from progressing.
  • Misoprostol: prostaglandin that can otherwise be used as an ulcer medication and as a cervical ripener
    • Misoprostol, taken 24–48 hours after mifepristone, works to empty the uterus by causing cramping and bleeding, similar to an early miscarriage.

Self-Managed Abortion

• Involves self-administering the same drugs that are used in medication abortion sanctioned by a provider
  • Mifepristone plus misoprostol
  • Misoprostol alone
• In medication abortion with provider involvement, mifepristone (200mg) is taken at a clinic, then misoprostol (800mg) is taken at home to finish the termination in private

Self-Managed Abortion

• Misoprostol alone is effective in ending a pregnancy before 12 weeks 80-85% of the time
• Mifepristone plus misoprostol is effective in ending a pregnancy before 10 weeks 95-98% of the time
• Some global health groups have distributed information about self-managed abortion as part of their SRHR work

How To Use Misoprostol-Only For a Medication Abortion

CRR on Self-Managed Abortion

• The legality & availability of self-managed abortion varies internationally.
• All surveyed countries do require a prescription for either mifepristone or misoprostol

Opioid Crisis

• There were 2,125 overdose deaths in Massachusetts in 2023, or roughly 6 people per day
• Statewide deaths decreased 10% from 2022 to 2023, but the number of deaths in Boston increased
• Nationwide, drop in deaths
• Fentanyl is the primary drug implicated in overdose deaths, both in MA and nationally

Opioid Crisis in Massachusetts

• 2023 showed the largest single-year decrease in overdose deaths in 13 years, but fatalities rose for Black men WBUR 2024

Opioid Crisis in Massachusetts

• In 2022 there were 2,170 opioid-related overdose deaths where a toxicology screen was also available.
• Substances present
  • fentanyl 93%
  • cocaine 53%
  • alcohol 28%
  • benzodiazepines 27%
  • prescription opioids 11%
  • amphetamines 9%
  • heroin 6%
  • xylazine 5%

Drugs Present in Massachusetts Opioid Deaths Over Time

• Fentanyl, Cocaine, Alcohol, Benzodiazepine, Prescription Opioids, Amphetamine, Heroin, Xylazine

Fentanyl

• Potent synthetic opioid approved by FDA as an analgesic & anesthetic
• Approximately 50x effective as heroin & 100x effective as morphine
• Can be used alone or in conjunction with other drugs, including in cases where the individual does not know that the drugs they are taking include fentanyl
• Effects: relaxation, euphoria, pain relief, sedation, confusion, drowsiness, dizziness, nausea and vomiting, urinary retention, pupillary constriction, and respiratory depression.
• Overdose can cause stupor, changes in pupil size, clammy skin, cyanosis, coma, and respiratory failure leading to death.

Recent Changes to US Drug Policy

• Movement away from prevention and treatment focused approaches and towards an enforcement-heavy approach focused on cartel drug smuggling and controlling the US border, with tariffs threatened as punishment of both Mexico & Canada
• Closure of departments and layoffs within federal programs focused on drug prevention and treatment
• Clawbacks of federal grants to non-profit organizations
• Public health approach involves use of harm reduction approaches (safer injection sites, methadone clinics, needle exchange programs, naloxone training and administration

Naloxone (Narcan)

Xylazine

• Veterinary tranquilizer not approved for human use
• Central nervous system depressant that can cause drowsiness & amnesia, slows breathing, heart rate, & blood pressure to dangerous levels
• Often used in combination with fentanyl & other opioids
• Because it is not an opioid, naloxone is ineffective in treating the impact of xylazine on breathing
• Using naloxone is still recommended in cases of suspected xylazine overdose because of likelihood of coinciding use of opioids
• Xylazine-involved overdose deaths have spread westward in the US, with highest concentrations in the Northeast 2024