ID Epidemiology Flashcards
what is an epidemic?
when does it become a pandemic?
epidemic:
an outbreak; an increase in numbers of cases of an infection over and above expected levels
OR
a single case, or small number of cases of an unusual organism
pandemic: epidemic that travels (epidemic with passport)
whats the difference between epidemic and endemic?
An endemic is a disease outbreak that is consistently present but limited to a particular region. This makes the disease spread and rates predictable. e.g. malaria in SSA
epidemic: an unexpected increase in the number of disease cases in a specific geographical area.
what is
a) incidence (& incidence rate)
b) prevalence?
a) incidence: measure of probability of infection. infection rate is no. of new cases per pop. at risk in given time
b) prevalence: proportion of infection found to be affecting a particular pop.
X conveys information about the risk of contracting the disease, Y indicates how widespread disease is:
what are X and Y?
incidence conveys information about the risk of contracting the disease, prevalence indicates how widespread disease is:
what are different modes of transmission? for ID
what is the first case called of transmission?
what is a primary case?
what is a clinica and sub-clinical case
- *index:** first case identified
- *primary case:** the case that brings infection into population (also get 2/3 cases)
- *sub-clinical case:** transfer virus to cases
- *clinical:** where symptoms and virus spread (could be 1/2/3 people)
what are factors that influence disease transmission?
what are 6 e.g. of resp. tract infections (viruses)
- resp. syncytial virus
- influenza
- COVID
- adenovirus
- rhinovirus
- nipah
which resp. viruses stay in upper resp tract? (4)
which resp. viruses go to low resp tract? (3)
infections of upper resp. tract
- rhinitis: inflammation of the nose
- pharyngitis: inflammation of the pharynx
- laryngitis: inflammation of the larynx
- conjunctivitis: inflammation of the mucus membrane of the eye
infections of lower resp. tract:
- croup: swelling of trachea (causes barking cough)
- bronchilotis
- pneumonia
how does a bacterial superinfection occur?
viral resp tract infections followed by bacterial superinfection:
- *-mucociliary escalator** (moves mucous out of lungs to be expelled by coughing) **damaged
- **viral infection OR inflammation can damaeg mucociliary escalator
- mucous not expelled
- followed by bacterial superinfection
how u diagnose resp. tract infections? (2)
what is a ct value / high or low ct value?
PCR - using a nasal pharyngeal swab:
- nucleic acids from virus is picked by virus panel -> recognise the viruses
- (can also check for bacterial panel to d/c if pneumonia is bacterial)
- ct value: no. of rounds of replication required to ID virus on swab
- high ct value: need lots of rounds of replication (low virus no.)
- low ct value: need few rounds to detect to virus
what is order, family, subfamily and genus of COVID?
how are coronaviruses diviied?
what were the intermediate hosts for SARs CoV-1, MERS, SARs CoV-2?
- *order:** Nidovirales
- *family:** Coronaviridae
- *subfamily:** Coronaviridae
- *genus:
- alpha coronavirus:**common colds (HCoC-NL63, HCoV-229E
- *- beta coronavirus:** common colds (HCov-HKU1/0), worse: (SARs CoV-1, MERS, SARs CoV-2)
(what could have been the intermediate host for covid?)
unsure atm, could be:
- fish market
- civet cat
- racoon dog
- snake
- pangolin
whats the difference between droplet and airbourne transmission?
- *droplet t:** larger, coughs and sneezes can spread droplets of saliva and mucus.
- *airborne t:** tiny particles (e.g. produced by talking), are suspended for longer. travel further
what are clinical features / symptoms of ebola?
what % of world is infected by influenza (yearly?)
- how many severe cases / deaths/
symptoms? whats a major difference between COVID?
- yearly infections: 15-20% of world pop
- 3-5m severe cases = 250 - 500 000 deaths a year
symptoms: (see pic)
- vs COVID: v. similar, but instead of total loss of taste and smell in covid, influenza is more stuffy.
-
describe the genome of influenza / how this influences transmission?
what is transmission cycle like?
genome: segmented - many different parts are expressed on individual nucleic acid pieces: if two viruses infecting the same cell -> pieces swap around (reassortment) and get new varients
what is influenza virus structure like?
what is influenza virus serology like?
- *- Orthomyxovirus (family)**
- enveloped
- surface spikes: Hemagglutinin protein (HA) (16 types), Neuraminidae protein (NA) (9 types)
- SS(-)RNA
- 8 segmented genes
- *- serology:**
- A = humans, animals and birds
- B = humans only (more chill)
- C = humans only (more more chill - mild resp. tract infections)
how does influenza change / involve?
- *point mutations**
- single point mutations only genome - change antigen
- most meaningful mutations occur in HA1 protein
- *antigenic shifts:**
- mixing of genomes: genetic reassortment between circulating human and animal strains. creates novel H/N combinations
- accounts for emergence of new strains of virus
- only in type A
what do u know about zika virus?
vector?
initial disease profile?
when were there outbreaks?
- serological detection through Africa and Asia, but no outbreaks < 20 cases in over 50 yrs
- vector: mosquito
