Microbio Week 10 - How Viruses are Transmitted & Cause Disease (Exam 3) Flashcards
Number of new infections over a period of time
Incidence
Total number of people infected in a population, new and old, over a period of time
Prevalence
Expected number of cases in a population. This number can be high, low, or even seasonal
Endemic
An increase in the average number of cases in an area
Epidemic
An epidemic that has spread to several countries or continents
Pandemic
On average, how many people one infected person will infect in a susceptible population
R0-Reproductive number
Spread in a population where not everyone is susceptible
Effective reproductive number (Re or Rt)
_____ is fixed, but ____ can change with changing variables such as social distancing, mask-wearing, immunity by infection, or vaccination
R0; Re
When people talk about getting R below 1, they are talking about ____
Re
An infectious disease transmitted from one source to another
Communicable
Name the 3 ways an infectious disease can be transmitted from one source to another
- Person to person
- Animal to person
- Fomite to person (phone, pen, shopping cart handle, etc)
Infections derived from contact; considered a very communicable disease spread by contact or proximity to an infected person
Contagious
What 3 ways are contagious infections transmitted?
- Respiratory droplets
- Fecal/oral
- Contact with skin or abrasion
Infections that are still communicable, but not by casual contact
Non-contagious
What 6 ways are non-contagious infections transmitted?
- Sexual contact (semen, vaginal fluid, lesions)
- Parenteral/injection (shared needles, needle stick)
- Congenital (transplacental)
- Perinatal (during or shortly after birth)
- Arboviral (mosquito, tick)
- Zoonotic (infected animals to humans)
Contagious or non-contagious?
Ebola
Contagious
Contagious or non-contagious?
Gastroenteritis
Contagious
Contagious or non-contagious?
Respiratory infections
Contagious
Contagious or non-contagious?
HIV
Non-contagious
Contagious or non-contagious?
HBV
Non-contagious
Contagious or non-contagious?
HCV
Non-contagious
Contagious or non-contagious?
Sexually transmitted infections
Non-contagious
Contagious or non-contagious?
HSV-1 and HSV-2
Non-contagious
Contagious or non-contagious?
Arboviruses
Non-contagious
Contagious or non-contagious?
HPV
Non-contagious
Contagious or non-contagious?
Zika
Non-contagious
Contagious or non-contagious?
Dengue
Non-contagious
Contagious or non-contagious?
Yellow fever
Non-contagious
Season for many viruses that are enveloped and transmitted through respiratory route and many gastroenteric viruses
Winter/Spring
Peak season for arobviruses (peak in mosquito vectors) and picornaivruses
Summer/early Fall
Time from infection until symptoms appear
Incubation period
Person is infected, but no virus is shed from the body
Latent period
Time from infection until one becomes infectious and capable of spreading disease to tohers
Latent period
Infected individual can spread disease to others
Infectious phase
Can a person be infectious before symptoms appear?
Yes!
Can a person stop being infectious before symptoms resolve?
Yes!
Can a person remain infectious after symptoms stop?
Yes!
Generalized symptoms that occur in many viral infections before specific symptoms arise that might aid in diagnosis
Prodromal phase
What is this an example of?
In measles, a person feels sick before the measles-defining rash
Prodromal phase
In most infections, the majority of people infected are __________ or ___________ infected
asymptomatically; subclinically
T/F: People who are asymptomatically or subclinically infected have no symptoms, but can spread disease - but not as well as those who have symptoms
True
What 3 factors determine the severity of infection?
- Age
- Immune status
- Genetics
T/F: Infections in children are always worse than the general population
FALSE, infections in children can be worse or sometimes better than the general population
Why are infections in people over 65 usually worse than the general population?
Immune system doesn’t work as well
Other health problems can make infections worse
Which patients have a much worse outcome with infections that can be relatively benign to the general population?
Immunocompromised
What can prevent infection or lead to milder symptoms?
Prior exposure by vaccine or previous infection
What can be a factor in disease severity?
General health of host
What makes certain people more or less susceptible to disease?
Genetic determinates
What is the most common form of transmission?
Human to human
Name the 2 types of human to human transmission
- Horizontal
- Vertical
What is the most common type of transmission from human to human?
Horizontal
Mother to infant, either in utero or during birth
Vertical
Spread of disease from a non-human reservoir to a human host
Zoonotic
Name the 2 types of zoonotic transmission
- Indirect
- Direct
Infection spread by insect intermediary called “the vector”
Indirect zoonotic
Infection spread by infected non-human animal to the human
Direct zoonotic
Virus is present in blood
Viremia
Localized or generalized (systemic) infection?
Doesn’t spread throughout body; no viremia. Some but not all infections of the respiratory tract, GI tract, eye, skin
Localized
Localized or generalized (systemic) infection?
Shorter incubation times, usually days
Localized
Localized or generalized (systemic) infection?
IgA is usually important
Localized
Localized or generalized (systemic) infection?
Not always lifelong immunity, sometimes shorter mucosal immunity
Localized
Localized or generalized (systemic) infection?
Spreads through the body via blood (viremia) or nervous system
Generalized (systemic)
Localized or generalized (systemic) infection?
Longer incubation times, weeks to months
Generalized (systemic)
Localized or generalized (systemic) infection?
IgG is more important
Generalized (systemic)
Localized or generalized (systemic) infection?
Usually lifelong immunity
Generalized (systemic)
All infections with viruses have what phase?
Acute phase (asymptomatic or symptomatic)
What are the 3 outcomes of the infection after the acute phase?
- Virus cleared from body
- Latent with virus only present if reactivated
- Chronic
For a chronic infection, is there a higher or lower virus level in the body than in acute phase?
Lower virus level
T/F: There can be a chronic infection in which the person never develops symptoms after acute phase
True
T/F: There can be a chronic infection in which the person develops symptoms months to years after acute phase
True
A new virus is spreading in the US. It is spread very efficiently by needle sharing and sex. The CDC has come out with the news that, on average, each sick person is infecting 2.5 people.
What is the type of transmission?
What is the reproductive number?
Transmission = non-contagious
Reproductive number = 2.5
What infection would lead to the lowest incidence in the general population over one month?
a. An acute respiratory infection
b. An acute gatroenteritis infection
c. A chronic infection, sexually transmitted
d. A chronic infection spread by IV drug use
d. A chronic infection spread by IV drug use
You are standing next to a person in an elevator who is sneezing and coughing. You have too much to do to get sick and hope that the person did not just transmit their disease. If you get sick, what type of transmission would it be?
Horizontal