Epidemics and Pandemics: Macrodrivers, Preparedness and Response

what is an epidemic

Illness or health-related events in excess of normal expectations

what is an outbreak

like epidemic but more localised event in time, place, or population

what is a pandemic

what is a pandemic

An epidemic occurring worldwide, or over a vast area

endemic is

when cases occur constantly at an expected level

syndemic is

Adverse interaction of 2+ epidemics, made more harmful by social and economic inequities.

Public health emergency of international concern WHO definition

An extraordinary event which is determined to constitute a public health risk to other States through the international spread of disease and which potentially requires a coordinated international response

PHEIC situation involves

serious, sudden, unusual, or unexpected

carriers implication for PH beyond the affected states national border

may require immediate international action

incubation period

Time between infection and symptom onset.

latent period

Time between infection and the start of infectiousness — when the person begins transmitting the infection.

basic reproduction number R0

the average number of secondary cases arising from a single primary case in a totally susceptible population

R0 is a measure of -

transmissibility - how likely an infection will spread in a population

R0 depends on -

biology of the pathogen, duration of infectiousness, infectious dose, population density, population, mixing patterns

example of syndemic

covid 19 and obesity

recent epidemic

Marburg Ethiopia

higher the R0 value =

shorter duration

R0>1 =?

Epidemic

what is SIR model

Susceptible, infectious, and recovered population

herd immunity

indirect protection effect of herd immunity; protects susceptible individuals

herd immunity threshold

the proportion of a population that must be immune to stop sustained transmission of an infectious disease

how can there be a herd immunity

prior vaccination or prior infection

what causes epidemic and pandemics

emerging infectious diseases and re-emerging infectious diseases

emerging infectious diseases (EIDs)

diseases that have newly appeared in a population or are increasing in incidence or geographic range

re-emerging infectious diseases (Re-EIDs)

diseases that were previously under control but are resurging due to ecological, environmental, demographic, or behavioural changes

herd immunity threshold

randomly mixed in population, high R0=high HIT

Epidemics/pandemics caused by -

microbes - emerging or re-emerging

newly evolved strain of a known pathogen

MRSA

A pathogen previously present at low (non-epidemic) levels, now increasing

Lassa, Mpox

a pathogen exploiting a new transmission opportunity

Nipah, Hendra

a pathogen new to human or animal populations

HIV, MERS-CoV

A known organism adapted to infect humans

Swine flu, influenza A/H1N1

predicting the unknown

avian influenza (H5N1, H7N9) Endemic in wild birds and outbreaks in poultry and mammals

risk of reassortment or mutation - human to human transmission

predicting the disease X

A serious international epidemic caused by a pathogen currently unknown to cause human disease

some epidemics arise from resurging diseases due to -

poverty and inequity (TB, Typhoid fever, Malaria)

conflict and displacement (cholera, measles, malaria, polio)

low vaccine coverage (measles, diphtheria, polio)

low vaccination coverage (polio, measles, pertussis)

weak health systems (cholera, Lassa fever, malaria)

new disease x predicted to be what virus

RNA virus, risk of genetic mutation

drivers of emergence - new enemies

systems - climate change

polio in Gaza - war and displacement

new enemies

spill over from the animal kingdom (zoonosis)

zoonoses and e.g.

infections acquired directly or indirectly from animal reservoirs that cause clinical disease in humans

Rabies, Hendra, Anthrax

emerging infectious diseases and e.g.

evolution of microorganisms from nature resulting in human-to-human infections which are independent from animals

HIV, Ebola, Yellow fever

zooanthroponosis and e.g.

infections transmitted from humans to animals

mycobacterium tuberculosis

ecosystem of pathogen emergence

pathogen flow at the wildlife-livestock-human interface

emerging pathogens arise where -,-&- systems intersect

environmental, ecological and human systems

increase wildlife-human interaction due to

land use change (deforestation, agriculture, mining)

_amplifies spillover risk

livestock intensification

what increases pathogen shedding

biodiversity and species loss

spread of pathogens across large distances

human mobility and trade

modern biomass

mostly humans and domesticated animals - amplification of risk

Marburg virus disease spread by what animal

Egyptian fruit bats

bats from mine was infected with

5000 bats infected with Marburg or Ravn virus

high animal density and stress

increased pathogen shedding and susceptibility

cross-species contact

viral mixing, spillover, and adaptation

wildlife and intensive farming

linked to SARS, avian influenza, and COVID

concentrated animal feeding operations are

high density, genetically uniformed population

breeding for rapid growth and high yield

stressful, crowded environments

efficient amplification hosts

industrialised diets

increase population susceptibility to severe infections

UPF environment

driving global obesity and metabolic disease pandemic

what impairs immune function (food)

obesity and metabolic dysfunction

obesity and metabolic syndromes linked to

higher hospitalisations

ICU

Mortality

COVID-19

H1N1 influenza

more connected world

pathogens travel at the speed of planes and supply chains

climate change divers for pathogens

rising temperatures (Zika, Malaria, Chikungunya, Lyme disease)

changing temperature and humidity (longer dengue and malaria seasons)

extreme weather events (outbreaks of cholera)

climate-driven migration and food security

next pathogen most likely to be (x5 points)

zoonotic virus

RNA virus

High-risk interfaces

High R0 and pre-symptomatic transmission

Most likely respiratory pathogen

next pandemic will be impacted by (x4)

speed of detection, data sharing, and transparent reporting

strength of health systems, research networks, global coordination

levels of public trust and vaccine acceptance

equitable access to vaccine, diagnostics, and therapeutics

global vaccine preparedness initiatives

CEPIs- develop vaccine against emerging pathogens within 100 days of identifying

focus on priority pathogens (Lassa, Nipah, Chikungunya)

develop platform technologies to enable rapid adaptation and multivalent formualtion

preparedness means -

building vaccine library and manufacturing capacity before the next outbreak

challenges of vaccine r&d

scientific and regulatory

scientific challenges

balancing speed with safety

rare and unpredictable outbreaks

difficulty identifying immune correlates of protection

reliance on animal models and immunobridging studies

regulatory challenges

traditional licensure require large-scale efficacy data

alternative regulatory pathways

FDA

Emergency Use Authorisation or Conditional Marketing Authorisation during health emergencies

WHO Emergency Use Listing

Ebola development

EBOVAC 1&3 2-dose regimen

EBOLA development lessons learnt

vaccine research can be done ethically and rigorously during outbreak

community trust and local engagement is necessary

early investment in preparedness trials and research capacity enables faster, safer responses to future epidemics

one health approach

moves us from crisis response to proactive prevention

one health approach share

surveillance and data across agriculture, health and environment

Africa CDC one health strategy

FAO-OIE-WHO-UNEP

Strengthening health systems and resilience

reducing vulnerability to epidemics

how to strengthen health systems

universal health coverage and strong primary health care

early detection and laboratory capacity in all region

data sharing and transparency

address social determinants - poverty, food security

epidemics and pandemics are shaped by

human-environment interaction

what intensifies the conditions for pathogen emergence and spread

industrialisation globalisation and climate change

preparedness is —

vaccines, surveillance, rapid response systems and equity, communication, and public trust