Lec 14 - Emerging viral diseases

Question 1

What is an emerging virus?

Answer 1

Causative agent of new/unrecognised virus infection

Question 2

What is zoonoses?

Answer 2

Human infection by virus pre-exisiting in stable non-human relationship

Question 3

Describe a stable virus-host interaction.

Answer 3

• Both host and virus survive and reproduce
• Dynamic fragile equilibrium
• Virus can evolve if host still able to control it

Question 4

Describe an evolving virus-host interaction.

Answer 4

• Unstable and unpredictable
• Selection to both host and virus
• Developed increased virulence/transmission from stable interaction

Question 5

Describe a dead-end virus-host interaction.

Answer 5

• Virus not transmitted to other hosts in species
• Multiple hosts can maintain/transmit virus or become dead-end hosts
• Severe disease but little transmission

Question 6

Describe a resistant host virus-host interaction.

Answer 6

• Host completely blocks infection from any/all levels of immunity
• Virus can’t rep or cleared
• No adaptive activation = asymptomatic

Question 7

How is incidence calculated?

Answer 7

Number of people infected divided by population

Question 8

How is morbidity calculated?

Answer 8

Number of people ill/symptomatic divided by number of infected

Question 9

How is mortality calculated?

Answer 9

Number of deaths divided by number of infected

Question 10

How is the case-fatality ratio calculated?

Answer 10

Number of deaths divided by number of ill/symptomatic

Question 11

How do rodents contribute to animal-human transmission? What disease do they often cause? List example viruses.

Answer 11

• Haemorrhagic disease
• Persistent/endemic in rodents with shedding but little symptoms
• Sin Nombre, Junin, Lassa

Question 12

How do bats contribute to zoonotic diseases? How are bats asymptomatic but humans have severe illness? List example viruses.

Answer 12

• Reservoirs for many dead-end infections but bats have little symptoms
• High virulence makes study difficult
• Bats have constant IFN-a activation vs humans activate IFN-a during infection
• Hendra, Nipah, rabies, Ebola, SARS coronavirus

Question 13

What strain of influenza is involved in cross-species transmission? How is it transmitted? Where is it found now?

Answer 13

• H5N1 from stable asymptomatic avian reservoir
• Transmitted by direct contact, fomites, airborne
• Found in Northern America and in raw milk from dairy cattle enhance virulence/transmission

Question 14

List social parameters influencing viral transmission.

Answer 14

• Dams and irrigation
• Deforestation
• Rerouting wildlife migration and wildlife parks
• Global travel
• Urbanisation
• ACs, used tires, day cares, hot tubs
• Blood transfusions and organ transplants
• Drugs and sex
• Bushmeat
• Farms, zoos, pets = sharing resources
• Host to the same vector
• Encroachment into habitats

Question 15

Describe the transmission and interactions of SARS-CoV-1. Why was it easier to control than the recent SARS-CoV-2 pandemic?

Answer 15

• Severe atypical pneumonia seen in 26 countries with highest mortality rates in those below 6yo and above 65yo
• Superspreaders = able to infect 10+ people
• Horseshoe bat reservoir infected masked palm civets acting as amplifying hosts
• Easier to control bc infectious when symptomatic

Question 16

Describe the transmission and interactions of MERS-CoV.

Answer 16

• Transmitted from bats to dromedary camels to humans
• Superspreader phenomenon seen in South Korea
• Easy to control bc infectious when symptomatic

Question 17

Describe the transmission and clinical presentation of Monkeypox/Mpox.

Answer 17

• Chimps and humans either had diffuse rash or singular lesions on face
• Orthopoxvirus that became international public health emergency