Upgrade to remove ads
Only $35.99/year

PUBH 401: Midterm 1

Terms in this set (146)

epidemiology
the study of the distribution and determinants of health-related states or events in specified populations and the application of this study to control of health problems
primary prevention
preventing the initial development of a disease in a person who is well and does not yet have the disease
primary prevention examples
- immunizations
- reducing exposure to certain risk factors
secondary prevention
identifying people who already have the disease but are not yet showing symptoms and then working to reduce the severity and potential complications
secondary prevention examples
- mammography screening for breast cancer
- testing stool for colon cancer
tertiary prevention
preventing complications in those who have already developed signs and symptoms of the disease and have been diagnosed
tertiary prevention examples
- rehabilitation for stroke victims
- anti-viral medication for shingles
fomite
any inanimate object that when contaminated with/or exposed to infectious agents, can transfer disease to a new host
fomite examples: 3 factors
door knob, clothing, money
vector
an arthropod that carries a disease-causing organism to new hosts
mechanical vector
a vector upon which an organism is transported but the organism does not go through aspects of its life cycle while in contact with this vector
mechanical vector example
a house fly transporting E. coli
biological vector
a vector in which an organism goes through part of its life (e.g. replicates)
biological vector example
mosquito and malaria
portal of exit
where the infectious agent leaves an infected human
portal of entry
where the infectious agent enters an un-infected human
clinical disease
disease showing signs and symptoms
subclinical (inapparent) disease
diseases not clinically apparent and not destined to become clinically apparent (needs to be diagnosed by antibody response or culturing organism)
subclinical (inapparent) disease: example
tuberculosis
isolation
the action of isolating or condition of being isolated / isolation of a virus -put the patient in isolation
quarantine
to put or hold in isolation to prevent the spread of disease
chronic carrier
a person who has the disease organism, but is not considered "infected" as measured by antibody response and does not show signs of the disease; however, this person can infect others
- can be over a time of few months or years
chronic carrier examples
Typhoid Mary, she caused at least 10 typhoid fever outbreaks; fecal and oral spread, not every organism can be a chronic carrier
occurrence of disease: when taking the first steps to investigate a possible epidemic, we ask three things:
1) who? was attacked by the disease
2) when? did the disease occur
3) where? did the cases arise
who? looking at characteristics of the human host such as age, sex, or race
- sharp decline in gonorrhea (1990-1996)
- after 1996, plateau
- rates for men and women are the same after 1996
when? some diseases occur with periodicity (cyclic)
- peak/trough
- education awareness during peak time (late spring, early summer)
- cyclic peaks is important to understand when there might be an endemic or epidemic
where? disease is not randomly distributed in time or place, there is often clustering
- federal government provides funding in high density areas, signs and education for lime disease
endemic
habitual presence of a disease within a given geographic area
pandemic
worldwide epidemic
epidemic
occurrence in a community or region of a group of illnesses clearly in excess of the normal expected number and derived from a common or propagated source
disease outbreak characteristics:
- explosive: sudden and rapid increase in number of cases
- cases limited to those who have a common exposure
- in food borne outbreaks, rare person to person transmission
factors affecting an outbreak of disease: (2)
- number of susceptible people: affected by deaths, people leaving the area, immunity
- herd immunity
herd immunity
- the resistance of a group of people to an attack by a disease to which a large proportion of the members of the group are immune
- can't for food-borne outbreaks
certain conditions must be met for herd immunity to exist: 5 factors
1) disease agent must be restricted to a single host species (humans only)
2) transmission must be relatively direct (person to person)
3) a person cannot be re-infected with disease; once they get it, they can't get it again
4) there should be random mixing in the population
5) for a given disease, we need to meet the vaccination threshold
reasons for no herd immunity:
1) choosing not to get vaccinated because of personal or religious beliefs
2) non-random mixing in the population
incubation period
the time interval between exposure to an infectious agent and the appearance of the first signs
during the incubation period, a person feels:
well and does not show signs of the disease; the organism is usually replicating, but hasn't gotten to a critical mass required to produce symptoms in the host
the length of the incubation period can be affected by: 3 factors
1) the body site at which the organism replicated (deep in the body vs. the surface of the skin)
2) the dose of the infectious agent the host received
3) how well the host's immune system functions
portals of entry examples
1) respiratory tract - mouth, nose
2) genitalia - vagina, penis
3) alimentary canal - mouth (from stomach)
4) other - eyes, broke skin
portals of exit examples
1) respiratory tract - mouth, nose (from lungs)
2) genitalia - vagina, penis
3) alimentary canal - anus (from intestines), mouth (from stomach)
4) other - eyes, broken skin
incidence
the rate of occurrence of new cases of a particular disease in a population being studied
incidence definition 2
the number of new cases of a disease that occur during a specified period of time in a population at risk for developing the disease
prevalence
the number of affected persons present in the population at a specific time divided by the number of persons in the population at that time
prevalence measures:
the burden of disease in a community
prevalence is useful for measuring: (2 factors)
- diseases where the onset (incidence) is difficult to determine
- health status
prevalence example: asthma
- 4 year period
- this is a rate = percent = per 100
- dark states have higher prevalence of asthma
- different air quality = higher rates
- more people move to states with asthma
prevalence example: obesity
lifestyle, diet, physical activity are all factors that influence health status of individuals
prevalence example: arthritis
- how many clinics needed
- type of rehabilitation services
- how many and what type of health professionals needed
prevalence (4 factors)
1) prevalence can be viewed as a snapshot of a population at a point in time
2) we don't know when the disease developed so we don't know anything about duration
3) therefore, the numerator of prevalence includes a mix of people with different durations of disease
4) it's not a measure of risk
morbidity measures:
the relative incidence of disease
surveillance (CDC)
ongoing systematic collection, analysis, and interpretation of health data essential to the planning, implementation, and evaluation of public health practice closely integrated with the timely dissemination of these data to those who need to know
passive surveillance
database set up for reportable diseases or there is a requirement for district health officers / clinicians to report a disease
active surveillance
- project staff make periodic field visits to health care facilities to identify new cases of a disease or deaths from that disease
- interview doctors, review medical records
objectives of epidemiology (3)
1) identify the etiology (cause of disease)
2) to determine the extent of disease in a community
3) to study the natural history and course of disease
objectives of epidemiology (2)
4) to evaluate new and existing preventive and therapeutic measures and modes of healthcare delivery
5) to provide the foundation for developing public policy regarding disease prevention and health promotion
examples of epidemiology In history: fluoride and dental caries (1) Kingston and Newburgh
- after observing that communities with higher water fluoride had lower rates of cavities, a trial was undertaken in two cities in upper Kingston and Newburgh
- one city received fluoridation in the water and the other did not
examples of epidemiology In history: fluoride and dental caries (2) Kingston and Newburgh
- after 10 years of water fluoridation, the results were in: city of Newburgh had lower rates of missing, filled, and decayed teeth bc they had fluoride in the water supply
examples of epidemiology in history: fluoride and dental caries (3)
- as fluoride content goes up, amount of dental caries per 100 children goes down
- communities that have more fluoride in their water have less dental caries
- lab calculated fluoride in the water content
- fluoride is healthy for your enamel
examples of epidemiology In history: fluoride and dental caries (4) Antigo, Wisconsin
- researchers calculated the average of decayed, missing, and filled teeth in 2nd, 3rd, and 4th graders
- for some reason, fluoride was taken out of the water in 1960
- in 1966: the amount of decayed, missing, and filled teeth increased significantly
examples of epidemiology In history: childbed fever (1)
- Ignaz Semmelweis and Childbed fever
- Many women died of childbed fever shortly after delivering a baby
- He noticed differences in maternal mortality due to childbed fever between two clinics
examples of epidemiology In history: childbed fever (2)
- First clinic had physicians and medical students who conduct autopsies in addition to delivering babies.
- Second clinic had only midwives (they didn't perform autopsies)
examples of epidemiology In history: childbed fever (3)
- Semmelweis observed that at First clinic, the doctors and students would go from working on cadavers to helping live patients.
- He implemented a policy of handwashing.
- Doctors and students had to wash their hands after working on autopsies and before handling live patients.
examples of epidemiology In history: childbed fever (4)
- Hand washing policy adapted broadly
- Now we know that streptococcal infection (bacterial infection) causes childbed fever. Bacteria were being transmitted from the dead patients to the live ones.
who was John snow?
- was a physician in London who spent several decades studying cholera in a systematic way
- "father of epidemiology"
- discovered why the outbreak of cholera occurred at the broad street pump
how did John snow go about investigating the broad street pump outbreak?
he looked into cases at the brewery, workhouse, surrounding areas of the broad street pump, and those who died from cholera
Where did Dr. Snow get the evidence to establish the existence of a local epidemic (that is, what was his source of death data)?
Dr. Snow got the evidence to establish the existence of a local epidemic from the general registrar.
Does removal of the pump handle seem to be a reasonable and responsible action? Why or why not?
- The removal of the pump handle seems to be a reasonable and responsible action.
- Removing the pump handle limits the rate of exposure of cholera for those drinking from the Broad Street pump.
- However, Snow did not believe that removing the pump handle was reasonable and responsible because people just moved away from the area of the pump.
Snow gives reasons to explain the six cholera cases who informants said had not drunk from the Broad Street pump. Do you think these are reasonable explanations...or wishful thinking considering what was known at that time about disease transmission? Explain.
- I think that these explanations were wishful thinking considering what was known at that time about disease transmission.
- This is because these six cases were unrelated to the Broad Street pump but they contracted cholera from other variables.
Snow focused on workers in the brewery because there were zero cholera deaths. Why did he find this unusual? (hint: do these observations support or discredit the theory of miasm). What factor(s) "protected" workers in the brewery from getting cholera?
- Snow found this unusual because the location of the brewery was close to the Broad Street pump.
- The factors that "protected" the workers in the brewery from getting cholera was that they barely drank water at all and there was a deep well in the brewery that provided the workers with water.
- The workers had no reason to drink from the Broad Street pump because of these factors.
Snow talks about the residents of the workhouse. Why did Snow focus on the workhouse? Explain the concept of observed versus expected cholera deaths in the workhouse.
- Snow focused on the workhouse because out of 535 inmates, only 5 died from cholera.
- However, if the mortality rate had been the same as that in the streets, upwards of 100 persons would have died.
- The concept of observed versus expected cholera deaths in the workhouse is that the observed cholera deaths was 5 and the expected number among inmates was 100.
- The expected number was determined by dividing the number of cholera deaths in the area surrounding the workhouse by the number of people living in the area surrounding the workhouse and multiplying it by the number of inmates.
What did Snow determine as the onset date of the Broad Street epidemic? Why did he choose this date?
- Snow determined the onset date of the Broad Street epidemic as August 31, 1854.
- He chose this date because nearly all of the 83 deaths had taken place in a short distance within the pump.
- The start of the outbreak followed the mode for fatal attacks and mode for deaths
Snow had the Broad Street pump handle removed on Sept. 8th. Looking at the Epidemic Curve (presented in slide 25), do you think removing the handle play a significant role in reducing the number of people getting sick? Yes or No?
- Yes, I think that removing the handle played a significant role in reducing the number of people getting sick.
- This is because there were no more than 5 attacks a day after the pump handle was removed on September 8th.
- After this date, the attacks per day were becoming significantly less
Complete this sentence:

Snow postulated that _________ ___ ____ _________________ played the biggest role in reducing the magnitude of the outbreak.
flight of the population
what do we know about cholera (biology) today?
- Incubation period: usually 1 -3 days, but can range from a few hours to 5 days.
- Symptoms last 2 -3 days sometimes up to 5 days.
- Infectious period: from onset of illness until a few days after recovery.
how do we treat cholera? 3 factors
- key is to prevent dehydration in the patient; replace fluid and salts lost through diarrhea.
- antibiotics can shorten the course of the disease and reduce the severity, but taking them is not as important as keeping the patient hydrated.
- vaccine is available outside the US.
how is cholera transmitted? 3 factors
- a person may get cholera by drinking water or eating food contaminated with the cholera bacterium
- in an epidemic, the source of the contamination is usually the feces of an infected person
- the disease can spread rapidly in areas with inadequate treatment of sewage and drinking water
what is cholera?
- bacterial disease transmitted by vibrio cholerae
- about 1 in 20 infected persons has severe disease
- approximately 25 - 50% of cases are fatal if untreated
what things play a role in the dynamics of disease transmission? 3 factors
1) host characteristics: age, sex, race, occupation, marital status, immune status
2) agent: biologic (bacteria.virus), chemical (alcohol, smoke), physical (trauma, smoke)
3) environment: temperature, crowding, water, food, air pollution
three modes of disease transmission
1) direct: person to person contact
2) indirect: common vehicle, single exposure, multiple exposure
3) vector: biological, mechanical
how are portals of entry/exit important in the control of infectious diseases?
in order to effectively control or prevent disease transmission in humans, the portal of exit and the portal of entry of the disease agent must be known
the following steps are required for disease transmission: 6 steps
1) an agent capable of infecting humans
2) a source: an infected host, or a reservoir of infection
3) a portal of exit from the source
4) a suitable means of transmission
5) a portal of entry into a new host
6) a susceptible host
how are chronic carriers for certain diseases important in the control of infectious diseases?
- Incubating carriers have been infected and can spread the pathogen, but do not yet show the symptoms of the illness.
- Convalescent carriers continue to spread the pathogen even though they have recovered from illness
how is herd immunity important in the control of infectious diseases?
once a certain number of people in a community are immune, the likelihood of an infected person meeting a susceptible person decreases
what are the steps needed to investigate a food-borne outbreak? (8 factors)
1) define the outbreak and validate the existence of an outbreak
2) examine the distribution of cases by time and place
3) look for interactions of relevant variables
4) develop a hypothesis/es
5) test the hypothesis/es
6) recommend control measures
7) prepare a written report of the investigation and findings
8) communicate findings to those involved in policy development and implement public changes if needed
how do you calculate an attack rate? (for those eating a specific item)
number of people who ate a food item and became ill / total number of people who ate the food item x 100
how to calculate incidence rate
number of new cases of a disease in the population during a specified period of time / number of persons who are at risk of developing the disease during that period of time x a base number (usually 1,000 or 100,000)
incidence rate: who should be in the numerator
number of new cases of a disease in the population during a specified period of time
incidence rate: who should be in the denominator
number of persons who are at risk of developing the disease during that period of time
incidence rate calculation:

Let's say we're in interested in the incidence rate of pink eye in Fullerton K-12 school district in 2014. We know that there are 14,000 students in the whole school district in 2014. The health officials for the school district counted 3,472 new cases of pink eye in 2014.

Then, the incidence rate for pink eye for 2014 in Fullerton school district students was: (use a base of 1000)
3472/14000 x 1000 = 248 per 1000 or 248/1000
time period for an incidence rate:
can be calculated for 1 week, 1 month, 1 year, 5 years, 10 years, etc.
because incidence rate measures the event of a person's transition from a non-diseased to a diseased state, the incidence rate is considered a measure of risk:
the incidence rate observes people at risk of developing a disease or health outcome through a defined time period
incidence rate: anyone who is included in the denominator must have the potential to become...
part of the group that is counted in the numerator
- examples: prostate cancer, measles
cancer incidence rates slide:
- lung / bronchus cancer between men and women
- differences in #2, rates = comparisons
- men have higher rates than women
- trends: incidence rates of bronchus cancer have gone down in the past 35 years
-- for women, they have increased
how to calculate prevalence rate
number of cases of a disease present in a population at a specified time / number of persons in the population at that specified time x a base number (usually 1,000 or 100,000)
prevalence rate: who should be in the numerator
number of cases of a disease present in the population at a specified time
prevalence rate: who should be in the denominator
number of persons in the population at that specified time
prevalence rate example: type 1 diabetes

We want to know the prevalence of type 1 diabetes among Fullerton school district children on September 1, 2015. There are 20,000 students attending school in the school district on Sept. 1, 2015. We ask school officials to survey their students on Sept. 1, 2015 and report the numbers who have type 1 diabetes. There are 227 cases.

Calculate prevalence rate of type 1 diabetes (use 100 as base), keep one decimal.
227/20,000 x 100 = 1.1 per 100 or 1.1/100
point prevalence
prevalence of a disease at a certain point in time
period prevalence
the number of people who have had at the disease during a certain time period
difference between incidence and prevalence
incidence: new cases
prevalence: existing cases
relationship between incidence and prevalence: prevalence is the flask, blue beads in the flask are incidence
- as incidence increases, so does prevalence
- people cured/ dying / no longer prevalent = prevalence decreases
- prevalence increases as new cases are identified
- prevalence decreases as people die of diseases
- prevalence is affected by incidence and by how long people live with a disease, die, or are cured
relationship between incidence and prevalence:
- incidence increases, prevalence increases
- duration increases, prevalence increases
- duration decreases, prevalence decreases
- incidence decreases, prevalence decreases
what formula can be used under steady-state assumptions?
prevalence = incidence x duration of disease

P = I x D
name the steady-state assumptions
- in-migration = out-migration
- disease rates are not changing
P = I x D example: TB

screened population: 1,000 in Hitown, 1,000 in Lotown
number with positive x-ray: 100 in Hitown, 60 in Lotown
point prevalence per 1,000 population: 100 in Hitown, 60 in Lotown

1) how was the point prevalence calculated?
2) which city appears to have a bigger problem?
1) 60/1000 x 1000 = 60/1000
2) Hitown
P = I x D example: TB cont.

screened population: Hitown, Lotown
incidence per year per 1000: 4 in Hitown, 20 in Lotown
point prevalence per 1,000 population: 100 in Hitown, 60 in Lotown
duration in years: 25 in Hitown, 3 in Lotown

1) calculate the TB incidence per year for Hitown and Lotown
2) which city appears to have a bigger problem?
1) - Hitown: I = P/D = (100/1000)/25 = 100/1000 x 1/25 = 100/25 = 4/1000
- Lotown = I = P/D = (60/1000)/3 = 60/1000 x 1/3 = 60/3 = 20/1000
2) Lotown because higher incidence rate AND people are living with TB longer in Hitown than Lotown
what is prevalence used for?
measures existing cases of a disease
what is incidence used for?
measures new cases of a disease
what can affect the accuracy of numerators in incidence and prevalence rate calculations?
1) defining who has the disease
-- what if different sets of diagnostic criteria are used?
2) ascertaining cases with interview data
-- respondent unaware of their disease status
-- respondent doesn't understand their disease status
-- inaccurate recall of episodes of illness
-- interviewer incorrectly records information
-- interviewer may ask questions incorrectly
-- interviewer may probe incorrectly based on prior knowledge of the hypothesis being tested
what can affect the accuracy of denominators in incidence and prevalence rate calculations?
1) inaccurate count
-- undercounting certain groups of the population (young men)
-- different ways of classifying ethnic groups
- potential to develop the disease of interest
what is disease surveillance?
used to monitor changes in disease frequency or changes in prevalence of risk factors by collecting incidence or prevalence data on select diseases/health states
what are the two types of surveillance?
active and passive
how are the two types of surveillance used?
they are used in health care facilities by project staff and databases
why do we need mortality rates?
- mortality can help us access disease severity
- mortality can help us determine changes in treatment effectiveness over time
- they are useful when there are problems identifying new cases of disease
-- may serve as a surrogate to incidence rates when the disease is severe and lethal
% of deaths =
proportionate mortality
mortality: cancer deaths slide
- frequency/count
- numbers increase
- over time, more people are dying from cancer/more people overall = population
cancer deaths =
number of people who died of cancer
cancer death rates =
number of people who died of cancer divided by the number of people in the population
which measure (cancer deaths or cancer death rates) can we use to assess the true magnitude of risk of dying from cancer?
cancer death rates
mortality rates are useful for comparisons by sex:
- lung cancer kills more men than women
- men's mortality rate = declining
mortality rates are useful for making comparisons by cause of death and age:
pharmaceuticals have decreased mortality significantly
types of mortality rates:
- only need to know how to calculate: annual all cause mortality or annual death rate
- can be combinations of above
- time must be specified for all mortality rates
annual all cause mortality: what is it measuring (formula)
total number of deaths from all causes in 1 year / number of persons in the population at midyear x a base (usually 1,000 or 100,000)
case-fatality: what is it measuring
- the percentage of people diagnosed with a disease that die from the disease
- measure of severity of disease
- measures benefits of a new therapy or technologies
case-fatality: formula
number of individuals dying during a specified period of time after disease onset or diagnosis / number of individuals with the specified disease x 100
case-fatality formula simplified:
# deaths / # individuals with disease x 100
proportionate mortality: what is it measuring
the proportion of all deaths in the US that can be attributed to a specific cause
proportionate mortality: formula
number of deaths from a specific cause in the U.S. in 1 year / total number of deaths in the US in 1 year x 100
proportionate mortality formula simplified:
# deaths from a specific cause (fatal) / total deaths (cases) x 100
calculation of mortality measures: example

Townville had a mid-year population of 200,000 in 2014; 75,000 are age 65 years or older and 125,000 are younger than 65 years of age. all data below are for 2014
- 2988 people, in total, die from all causes
- 20 are sick with pertussis in 2014
- 2 die from pertussis (out of the 20 who had it)
- 1900 people age 65 yrs or older die from all causes
- use a base of 1000 where appropriate

calculate: all cause-mortality rate in 2014
2988/200,000 x 1000 = 14.94 per 1000
calculation of mortality measures: example

Townville had a mid-year population of 200,000 in 2014; 75,000 are age 65 years or older and 125,000 are younger than 65 years of age. all data below are for 2014
- 2988 people, in total, die from all causes
- 20 are sick with pertussis in 2014
- 2 die from pertussis (out of the 20 who had it)
- 1900 people age 65 yrs or older die from all causes
- use a base of 1000 where appropriate

calculate: case-fatality rate for pertussis in 2014
2/20 x 100 = 10.00 per 100 or 10%
calculation of mortality measures: example

Townville had a mid-year population of 200,000 in 2014; 75,000 are age 65 years or older and 125,000 are younger than 65 years of age. all data below are for 2014
- 2988 people, in total, die from all causes
- 20 are sick with pertussis in 2014
- 2 die from pertussis (out of the 20 who had it)
- 1900 people age 65 yrs or older die from all causes
- use a base of 1000 where appropriate

calculate: proportionate mortality for pertussis in 2014
2/2988 x 100 = 0.07 per 100 or 0.07%
proportionate mortality, US 2009 slide
- dying of chronic disease as we age
- easy to misinterpret/draw people into your way of thinking
- in 2009, 25% of all deaths in the 25-44 yr age group were deaths due to accidents in the U.S.
years of potential life lost: what is it measuring
- measures premature mortality
- loss of future productive years
how to calculate YPLL:
1) for each cause of death, each decreased person's age at death is subtracted from a predetermined "standard" age = 75 years in the U.S.
2) sum the years of potential life lost for each individual to get the total YPLL for a specific cause of death
examples of YPLL calculations:

1) age of death = 20 yrs
2) aad = 57 yrs
3) aad = 83 yrs
4) aad = 4 yrs
5) aad = 71 yrs

total YPLL = ?
1) 75-20 = 55 YPLL
2) 75-57 = 18 YPLL
3) 75-83 = 0 YPLL
4) 75-4 = 71 YPLL
5) 75-71 = 4 YPLL

total YPLL = 148 yrs
years of potential life lost: functions in public health (3)
1) establishing research and resource priorities
2) surveillance of temporal trends in premature mortality
3) evaluating effectiveness of program interventions
Refer to figure 1-2 from Lecture 1. List three reasons, other than the ones I named in the lecture, that could explain why the top three causes of death have changed from infectious diseases (in 1900) to chronic diseases (in 2014). (hint: Think of all that has changed in the United States over the 114 year period.)
1) Medication
2) Diet
3) Sanitation
Many elementary schools (grades K - 6) provide education on the dangers of smoking cigarettes. They are hoping that once students understand the dangers, they will never start smoking. Why type of prevention campaign is this? Primary? Secondary? Tertiary? Defend your answer.
This is primary prevention because elementary schools are taking measures by educating children on the dangers of smoking cigarettes. By using this type of prevention, they are trying to prevent the initial development of a disease before the person has it. In this situation, educating children on the dangers of smoking will convince them not to smoke.
Why did the Second Clinic have lower maternal mortality rates than First Clinic?
The Second Clinic had lower maternal mortality rates than the First Clinic because the First Clinic had a source of disease transmission. The doctors and students in the First Clinic would go from doing autopsies to assisting other patients without washing their hands. The solution was implementing the policy of handwashing.
In 2020, 731 cases of West Nile virus (WNV) were reported in the United States, resulting in 66 deaths. California had 235 cases of WNV, and eleven of those cases died. Several cases were from Orange County. Based on the West Nile Virus CDC Handout, please answer the following.

What is the incubation period for West Nile Virus?
The incubation period for West Nile Virus is between 3 to 14 days after someone is bitten by an infected mosquito.
In 2020, 731 cases of West Nile virus (WNV) were reported in the United States, resulting in 66 deaths. California had 235 cases of WNV, and eleven of those cases died. Several cases were from Orange County. Based on the West Nile Virus CDC Handout, please answer the following.

Does West Nile Virus have subclinical cases? If so, how many?
West Nile Virus does have subclinical cases. From the handout, "approximately 80 percent of people who are infected with WNV will not show any symptoms at all" (CDC).
In 2020, 731 cases of West Nile virus (WNV) were reported in the United States, resulting in 66 deaths. California had 235 cases of WNV, and eleven of those cases died. Several cases were from Orange County. Based on the West Nile Virus CDC Handout, please answer the following.

What types of modes of transmission are being described? Be as detailed as possible.
The types of modes of transmission that are being described are indirect transmission through a biological vector. West Nile Virus is spread through indirect contact from an infected mosquito to other humans or animals when it bites. The infected mosquito is then a biological vector, in which it carries a disease-causing organism to new hosts and goes through part of its life cycle (i.e. replicates).
Write "the number '32' from the pie chart for 45-64 year olds in 2009 in a complete sentence.
In 2009, 32% of all deaths of those aged 45-64 were from cancer.
Is it possible to calculate suicide mortality rate for 25-44 years olds from the data on the chart?
no because you don't have the mid-year population in 2009 for the formula
Refer to Figure 4-7 and the corresponding table. Explain why the proportionate mortality for cancer decreases from 20% in the Early Period to 16.7% in the Later Period but the mortality rate for cancer stays the same in both Early and Later Periods.
- because the # of all deaths between the Early period and Later Period increases (the total amount of all deaths) from 80/1000 to 120/1000
- the total mortality rate has increased
Other sets by this creator