L1 - Infectious diseases Flashcards
Define antigenic shift
Antigenic shift: Genetic shift occurs when major changes in the HA or NA take place and a virus emerges which contains a haemagglutinin different from those of previously circulating viruses. This could be due to convergence of animal and virus genes. This leads to an epidemic.
Fraction of human infections that are estimated to have zoonotic origin
60-70%
Define zoonosis
An infectious disease of animals that can be transmitted to humans
State 5 zoonoses
Anthrax, avian influenza, cowpox, rabies, typhus
World population growth is expected to grow to approx. what figure by 2050
9 billion
What is the general trend for travel over successive familial generations
Increases
Describe difference in influenza rates between less and more developed mega-cities
More developed = lower rate of influenza
Less developed = higher rate of influenza
What is evolution driven by?
Generation time
Define generation time
The time for a female of a species to produce another female
Explain difference between pathogen and human evolution
Pathogens evolve much more quickly as they have a shorter generation time.
When did Homosapiens sapiens diverge?
100/200 000 years ago
What is the pathogen type that humans are most affected by?
Bacteria
Why are humans most affected by bacteria compared to other pathogens?
Jumping species barrier is easy for bacteria. The bacterial genome is very fluid. Genetic material can be transferred very easily and antibiotic resistance is very quick to come about.
Order world population by continent
Highest in Asia, then Africa, S. + C. America and Carribbean, Europe and N. America, Oceania
Explain significance of airline networks for infectious disease
Flight networks dictate pathogen spread. We know this by whole genome sequencing, and comparing the genomes of people with the disease to other parts of the world. People often fly during disease incubation period.
Where did H1N1 originate from?
Southern most point of North America
How did Hong Kong policy change to prevent spread of bird and human influenza virae?
Chilled dead chickens were transported into the city instead of live ones
Define “megacity”
> 10 million people
Where are antibiotic use in livestock not restricted?
USA, China, India
What countries have the highest chicken and livestock populations?
Europe, Australasia
What is SARS
Coronavirus
How did China deal with Beijing 2003 SARS outbreak?
Isolation camps around city periphery
How was SARS Beijing outbreak detected?
Internet, then WHO
What is the animal origin of SARS?
Bats. They are seen as a delicacy in E. Africa, Asia. Transmission is through semi-cooked meat.
When was WNV discovered?
1999 summer in US.
What have the effects of WNV been since discovery?
19000+ illness cases, 750+ US deaths (till 2009)
What is the animal host of WNV? What is the vector?
Animal host: bird
Vector: Mosquito
How many deaths does WNV cause on average per year?
750-1000
What is the animal origin of HIV?
HIV is acquired from primates
Why is HIV mutation rate high?
No proof-reading mechanism as is an RNA virus.
Describe epidemiology of malaria
Extremely prevalent in Central Africa, India, Nepal, South America. Low in colder countries.
What does MERS virus stand for? What is the animal host and transmission?
MERS = Middle East Respiratory Syndrome Coronavirus.
Animal host = camel, transmitted when humans come too close to their camels.
How was the Ebola epidemic in West Africa 2014-2015 controlled?
Contact tracing, isolation, quarantine. Volunteers from overseas helped. Aid was sent. Patients felt ill before highly infectious so were prevented from travelling.
How likely is Guillian-barre syndrome in those affected by ZIKA?
Affects adults. Is extremely unlikely 4/100 000.
How likely is microcephaly in ZIKA affected babies?
1% during first trimester of pregnancy
Where is ZIKA present?
Tropical locations: S. America, Caribbean
What are the urgent tasks to complete when a new disease emerges?
Indication (clusters of mortality/morbidity), identification of aetiological agent, development of diagnostic tests, determination of route of transmission, creation of clinical algorithms, activation of data capture systems, identify and implement public health measures, keep public informed
What is the significance of the basic reproductive number R0?
Must be larger than 1 to produce and epidemic. It is a key determinant of infection incidence and prevalence.
What is R0?
Basic reproductive number. Average number of secondary cases generated by 1 primary case in susceptible population.
What is Rt?
Total number of infectious cases caused by a new case occurring at time t.
Explain epidemic timescales
You have establishment of the new infection, with some stochastic effects. Then you have exponential growth followed by exhaustion of the susceptibles (so exponential decrease) and then the infection becomes endemic to the area so is stuck in an equilibrium higher than when it started.
What age group did H1N1 most affect?
6-15 years
What document houses a clear definition of Influenza control policy?
UK influenza pandemic contingency plan. Pandemic Flu.
How would you identify risk factors and co-morbidities during an epidemic?
Use first 500 cases.
What is EVD?
Sever illness caused by Ebola. Transmission is through bodily fluid.
What was the total number of Ebola cases in West Africa?
3685
What are the key stats for Ebola?
Disease: EHF/EVD Incubation period: 2-21 days Generation time: 10-12 days Doubling time: 4-5 days R0: 2-3.5 Survival rate 47-50%
Define antigenic drift
This is when there are minor changes in virus genetic code leading to differences in antigen. This leads to people who have immunity being affected by different strain of virus. Passive pathogen evolution.
