Lecture 9: Dynamics of Emerging Viral Diseases

Care of: Audrey

1. Globalization & Connectivity

2. Urbanization & Population Dynamics

3. Environmental & Ecological Changes

4. Microbial Adaptation

4 convergent forces of disease emergence

Globalization & Connectivity

A convergent force of emerging diseases characterized by increased interconnectedness of countries and fast air travel

Urbanization & Population Dynamics

A convergent force of emerging diseases characterized by crowded living conditions and limited access to healthcare and sanitation due to poverty

Environmental and Ecological Changes

A convergent force of emerging diseases characterized by increased human-wildlife interactions due to changes in natural habitats and deforestation

Environmental and Ecological Changes

A convergent force of emerging diseases characterized by the alteration of the distribution of diseases and their vectors due to changes in the environment like climate change

Microbial Adaptation

A convergent force of emerging diseases characterized by the evolution and adaptation of pathogens in new environments

Spillover

another term for zoonosis

Amazon North Region of Brazil

Home to 183 arthropod-borne and other vertebrate viruses

Dengue virus, West Nile virus, Noroviruses

Viruses emerging due to urbanization and human population growth

Ebola, Marburg, Influenza, Hantaan, Junin, Machupo, and Sin Nombre viruses

Viruses emerging due to zoonotic transmission

HIV, Human T-Lymphotropic Virus (HTLV)

Viruses emerging due to human-human transmission

Rift Valley fever, Influenza, Hantaan, Junin, Machupo viruses

Viruses emerging due to agricultural and environmental changes

Marburg virus & West Nile virus

Viruses with unknown or unclear emergence factors

Zoonotic viruses dominate,

Vector-borne viruses spread with environmental changes,

Social behaviors influence transmission

Major trends of emergence factors

Stable

In this interaction, the virus is maintained in the ecosystem

Evolving

In this interaction, the virus is passed to a naive population

Dead-end

This is a one-way interaction to a different species;

Dead-end Host

A host from which infectious agents are not transmitted to other susceptible hosts

Resistant host

This "host" blocks infections

naive population

A population of organisms that has never before encountered a specific pathogen

Eastern Equine Encephalitis

What does EEE virus stand for?

1. Encountering new host

2. Establishment and dissemination

2 steps of emerging infections

1. No entry points (lack of suitable receptors in cells)

2. Insufficient viral load

3. Immune defense

3 reasons for failed transmission of viruses

1. Direct contact with the bodily fluids of infected hosts

2. Sharing resources with different species

3. Sharing of insect and rodent vectors

4. Encroachment by one species into the habitat of another

4 Transmission Parameters

Poliomyelitis (Polio)

referred to as a disease of modern sanitation

Hendra virus and Nipah virus

2 paramyxoviruses isolated from flying foxes

Hendra virus

A type of paramyxovirus that is transmitted from flying foxes to horses, then horses to humans

Australia (September 1994)

The first outbreak of the Hendra virus occurred in ____

Malaysia (1998)

The first outbreak of the Nipah virus occurred in ____

Nipah virus

A type of paramyxovirus that causes respiratory and neurological diseases in pigs

Fruit bats (𝘗𝘵𝘦𝘳𝘰𝘱𝘶𝘴 𝘷𝘢𝘮𝘱𝘺𝘳𝘶𝘴)

This organism excretes Nipah virus in their urine

Amplifier Host

A host that supports rapid multiplication of the virus

Incubation Period

the duration between exposure to the virus and the onset of symptoms

malaise

a general feeling of discomfort

myalgia

muscle pain

2 to 10 days

the incubation period of SARS

Severe Acute Respiratory Syndrome

What does SARS stand for?

Guangdong Province, China (November 2002)

The first outbreak of SARS was first reported in ____

Horseshoe bats (𝘙𝘩𝘪𝘯𝘰𝘭𝘰𝘱𝘩𝘶𝘴 𝘴𝘱𝘱.)

Original reservoir of SARS-CoV

Himalayan Palm Civets (𝘗𝘢𝘨𝘶𝘮𝘢 𝘭𝘢𝘳𝘷𝘢𝘵𝘢)

Intermediate hosts of SARS-CoV-1 hypothesized to have passed the infection to humans

Wuhan, China (2019)

The outbreak of SARS-CoV-2 (COVID-19) first occurred in _____

RaTG13

This virus shares approximately 96% genomic similarity with SARS-CoV-2

Wuhan Institute Virology

Some theories suggest that SARS-CoV-2 escaped from this research facility

Public Health Emergency of International Concern

what does PHEIC stand for?

January 30, 2020

The WHO declared COVID-19 a Public Health Emergency of International Concern (PHEIC) on ______

March 11, 2020

The WHO declared COVID-19 a pandemic on ______

Host Range Jump

occurs when a pathogen crosses from one species to another