Lecture 24: The History of Epidemics

When was the first bacteria discovered

1665

Who discovered the first bacteria

Robert Hooke

How was the first bacteria discovered

Using very primitive microscopes

When was the first virus discovered

1892

How was the first virus discovered

Plants were filtered to remove the bacteria however were still getting infected so it was thought there was an even smaller organism causing disease

Where does prevention and control of disease come from

Understanding the mechanisms of transmission of pathogens to humans

What measures can be implemented to contain the spread of infectious disease

Isolation, quarantine, border control

What is recognised as a key component of outbreak response

Community engagement

What do you have to understand to understand transmission

The disease and the host

What virus carries smallpox

Varilla virus (poxvirus)

How many people die of smallpox

Around 30% infected

How is smallpox transmitted

• Person to person via droplets

• Contact with contaminated bedding or clothes

Incubation period of smallpox

2 weeks

Symptoms of smallpox

1. Starts with high fever, fatigue and severe back pain

2. Rash develops 2-3 days later with fluid filled pustules all over the body (now infectious)

3. Scabs fall off after 2-3 weeks

4. Recovery

How is there effective eradication of smallpox

• An effective vaccine

• Smallpox is a DNA virus and therefore doesn’t mutate as well as RNA viruses

• There are distinctive symptoms of smallpox infection

• The eradication process was really pushed - people were financially rewarded for turning in infected people

What did Edward Jenner do

Developed a working vaccine with no knowledge of virology or the immune system

In what way is cowpox similar to variola virus

Antigenically

What was vaccine virus

A related poxvirus to smallpox and subsequently used as a vaccine

When was the WHO smallpox eradication programme

1966-1980

Cholera bacterium

Bacterium vibrio cholerae

• Two serogroups, o1 and o139 responsible for outbreaks

How many people die of cholera

25-50% infected

How is cholera transmitted

Drinking water or food

What was the cause of a large cholera epidemic

Fecal contaminated water supply

Incubation period of cholera

2 hours to 5 days

Symptoms of cholera

• Profuse watery diarrhoea

• Vomiting

• Circulatory collapse

• Shock

What can prevent water-bourne viruses like cholera and typhoid

Supplying safe drinking water and proper disposal of sewage waste

What is the R number

The reproduction number is an epidemiological metric unit used to describe the contagiousness or transmissability of an infectious agent

How is the R number estimated

With complex mathematical models

What factors affect the R number

• biological

• Sociobehavioural

• Environmental

What is the R number if an outbreak is expected to continue and end

• >1 continue

• <1 end

R number of disease examples

• MERS = 0.8

• Influenza = 1.5

• Ebola = 2

• Covid-19 = 3

• SARS = 3.5

• Mumps = 4.5

• Smallpox = 6

• Measles = 12-18

Digital methods of outbreak surveillance

• Passive surveillance leads to delay in detection

• Social media can show outbreaks earlier

• Social media and internet searches show symptoms

Animal surveillance of outbreak

• “One health” approach

• Monitor sentinel species (e.g macaques)

Mathematical modelling surveillance methods of outbreak

• Predicting rate of increase of cases

• Plan ahead for required resources

• Understanding the effect of rising herd immunity

Methods of sharing information of outbreaks

• Online platforms; proMED-mail, Global Public Health Intelligence Network, HealthMap

• WHO’s early warning and response system (EWARS); a box of electronic surveillance equipment for rapid deployment

• Oxford-Nanopore minION; credit card size, powered from laptop USB connection, provide live maps of outbreak movement

How can bat hosts be used to predict the next pandemic

• Contain many novel viruses

• Nipah virus deaths have increased

• Marburg virus has a fatality rate of 88%

• Likely thousands of undiscovered coronaviruses in bats

What may virus hunting be used for

Expanding our knowledge of virus diversity

Where do more pathogens emerge from

Areas with high levels of human wildlife contact as the proportion increases when contact is between closely related species

What does computational modelling do

Assesses virus genetic similarity to human genome. It is around 70% accurate

What diseases does WHI predict may cause the next global pandemic

• Covid-19

• Crimean Congo haemorrhagic fever

• Ebola

• Marburg

• Lassa fever

• MERS-CoV

• SARS

• Nipah

• Rift valley fever

• Zika virus

What type of consequences do disease epidemics have

• Every aspect of our lives

• Religious

• Political

• Economic

• Social