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Epidemiology 3a Flashcards

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1
Q

What is Tajikistan?

A

Tajikistan is one of five Central Asian countries that were formerly part of the Soviet Union. It is one of the poorest of these countries, with less than 7% of its land available for cultivation.

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2
Q

What happened to Tajikistan in 1991?

A

Tajikistan became an independent nation in 1991 as the result of the dissolution of the former Soviet Union

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3
Q

Why did tajikistan become an independant nation in 1991?

A

As a result of the dissolution of the soviet union.

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4
Q

What was the problem for tajikistan of the dissolution of the soviet union?

A

The shift in its status from being a member of a totalitarian republic to an independent nation brought with it certain challenges.

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5
Q

What were the challenges for tajikistan as a result of becoming an independent nation?

A
  • Basic public services (e.g., health care, water supply, and sewer systems), previously guaranteed for even the poorest nations in the Soviet Union, were no longer supported through the Soviet cost-sharing system.
  • Financial hardships and inadequate tariffs in Tajikistan severely limited provision of services and maintenance of equipment.
  • Faulty design and installation of equipment while Tajikistan was still part of the Soviet Union added to these problems.
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6
Q

What caused even worse problems for tajikistan after becoming an independent nation?

A

To make matters worse, shortly after becoming an independent nation, Tajikistan experienced a civil war that continued until a cease-fire occurred in 1996

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7
Q

What happened during the civil war in tajikistan?

A

During the civil war, an estimated 50,000 lives were lost and 1.2 million persons were internally displaced. In addition, a substantial number of trained technical and professional workers left the country.

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8
Q

What happened by 1997 in tajikistan?

A

By 1997, the country’s economy and much of its infrastructure had collapsed. Consequently, the health of the people of Tajikistan suffered. Diseases rarely seen before the dissolution of the Soviet Union reappeared in increasing numbers.

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9
Q

What reappeared in tajikistan?

A

Diseases rarely seen before the dissolution of the Soviet Union reappeared in increasing numbers.

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10
Q

What caused the reappearance of diseases?

A

Lack of hygiene, access to (clean) water, nutrition problems, disease, population density.

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11
Q

What health problems are common in countries with displaced populations,
economic hardships, and deteriorating infrastructure?

A

malnutrition, waterborne diseases, and outbreaks of vaccine-preventable diseases like measles and cholera. Additionally, mental health issues such as anxiety and depression are also prevalent.

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12
Q

What did the primary health care offer in tajikistan?

A

The polyclinics provided ambulatory care and certain acute care services

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13
Q

What did the polyclinics in tajikistan lack?

A

Lacked surgical and post- operative care facilities. Limited hospital beds at nationally run hospitals were available for patients needing in- patient services

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14
Q

How were notifiable disease reported?

A

Cases of notifiable disease were reported each week from the polyclinics and hospitals to the Sanitary Epidemiologic Service (SES).

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15
Q

What is the Sanitary Epidemiologic Service (SES)?

A

the public health unit that monitored infectious diseases.

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16
Q

What was reported in feb 1997 in Dushanbe, the capital of tajikistan?

A

an increase in typhoid fever cases was reported in Dushanbe, the capital of Tajikistan (population approximately 600,000).

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17
Q

Details about the spread of typoid fever in dushanbe?

A

Typhoid fever was endemic in this area, more than 2,000 cases had been reported during January 29−February 11 (i.e., a 2-week period), compared with approximately 75 cases each week during the previous month. During the same 2-week period in 1996, only 23 cases had been reported.

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18
Q

Where were typoid fever patients hospitalized?

A

All typhoid fever patients were hospitalized at one of six full-service hospitals in the city, as required by a central government edict.

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19
Q

What did SES staff do in response to the increase in transmission of typhoid fever?

A

SES staff studied the situation to determine the likelihood of an outbreak.

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20
Q

Besides an outbreak, what are other possible explanations for the increase in cases of typhoid fever reported to the SES? How would you go about ruling out these other explanations?

A

Better tests, better labs, better diagnostic tools, better patient psychology.

Ruled out by conducting an investigation into the outbreak. Finding the cause of the outbreak.

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21
Q

What did SES investigators do as a first step in investigating the increase of typhoid fever?

A

SES investigators confirmed the diagnosis of typhoid fever in a sample of patients admitted to one of the Dushanbe hospitals. They also examined laboratory testing procedures and reagents at all six hospitals. No evidence of laboratory error or contamination of cultures was identified.

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22
Q

What did the SES investigators find in their investigations into the increase of typhoid fever?

A

SES investigators were unable to identify recent events that might have led to an increase in the completeness of
case reporting.

SES investigators noted that the civil war had resulted in the displacement of substantial numbers of Tajikistan citizens and an increase in the Dushanbe population. However, movement of the displaced persons was spread over a lengthy period and seemed an unlikely explanation for the sudden increase in typhoid fever cases during Jan−Feb 1997.

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23
Q

What did SES investigators conclude?

A

SES staff concluded that the increase in typhoid fever cases was real and likely represented an outbreak. Because previous typhoid fever outbreaks had been associated with foods and beverages sold by street vendors, the city government prohibited such sales. However, considerable debate remained about the source of the outbreak and appropriate control measures.

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24
Q

What was the first step of SES investigators?

A

to review known information about the disease and risk factors on the basis of its epidemiology and previous outbreaks.

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25
What is typhoid fever?
Typhoid fever is an acute, life-threatening febrile illness caused by the bacterium Salmonella enterica serotype Typhi. Paratyphoid fever is a similar illness caused by S. Paratyphi A, B, or C.
26
What bacterium causes typhoid fever?
Salmonella enterica serotype Typhi
27
What are the modes of transmission for typhoid fever?
Humans are the only source. No animal or environmental reservoirs have been identified. Typhoid and paratyphoid fever are most often acquired through consumption of water or food that have been contaminated by faeces of an acutely infected or convalescent individual or a chronic asymptomatic carrier. Transmission through sexual contact, especially among men who have sex with men, has rarely been documented.
28
Describe the occurrence of typhoid fever.
An estimated 22 million cases of typhoid fever and 200,000 related deaths occur worldwide each year; an additional 6 million cases of paratyphoid fever are estimated to occur annually. Approximately 400 cases of typhoid fever and 150 cases of paratyphoid fever are reported to CDC each year among persons with onset of illness in the United States, most of whom are recent travellers.
29
What areas are at risk of typhoid fever?
Risk is greatest for travellers to South Asia (6 to 30 times higher than all other destinations). Other areas of risk include East and Southeast Asia, Africa, the Caribbean, and Central and South America.
30
What are travellers to south asia at highest risk for?
Travelers to South Asia are at highest risk for infections that are nalidixic acid-resistant or multidrug-resistant (i.e., resistant to ampicillin, chloramphenicol, and trimethoprim– sulfamethoxazole).
31
Travelers who are visiting...
...friends or relatives are at increased risk of typhoid fever.
32
What does the risk of acquiring typhoid fever increase with?
increases with the duration of stay. although, travellers have acquired typhoid fever even during visits of less than 1 week to countries where the disease is endemic.
33
What is the incubation period of typhoid and paratyphoid infections?
The incubation period of typhoid and paratyphoid infections is 6–30 days
34
Describe the onset of typhoid fever symptoms.
The onset of illness is insidious, with gradually increasing fatigue and a fever that increases daily from low-grade to as high as 102° F–104° F (38.5° C–40° C) by the third to fourth day of illness. Headache, malaise, and anorexia are nearly universal. Hepatosplenomegaly can often be detected. A transient, macular rash of rose-coloured spots can occasionally be seen on the trunk.
35
Describe the fever symptom of typhoid fever.
Fever is commonly lowest in the morning, reaching a peak in late afternoon or evening
36
How long does typhoid fever last for untreated?
Untreated, the disease can last for a month.
37
How long does it take for serious complications of typhoid fever to begin?
The serious complications of typhoid fever generally occur only after 2–3 weeks of illness
38
What are some of the serious complications of typohid fever?
mainly intestinal haemorrhage or perforation, which can be life threatening.
39
What does infection with typhoid or paratyphoid fever result in?
Infection with typhoid or paratyphoid fever results in a very low-grade septicaemia
40
How often is blood culture found positive?
Blood culture is usually positive in only half the cases.
41
How often is stool culture found positive?
Stool culture is not usually positive during the acute phase of the disease
42
How often is bone marrow culture found positive?
Bone-marrow culture increases the diagnostic yield to about 80% of cases.
43
What is the Widal Test?
The Widal test is an old serologic assay for detecting IgM and IgG antibodies to the O and H antigens of Salmonella
44
Is the widal test reliable?
The test is unreliable, but is widely used in developing countries because of its low cost.
45
Why is the widal test used in deevloping countries?
widely used in developing countries because of its low cos
46
Are tests other than the Widel Test available?
Newer serologic assays are somewhat more sensitive and specific than the Widal test, but are infrequently available.
47
Why does the diagnosis of typhoid and paratyphoid fever need to be made clinically?
Because there is no definitive test for typhoid or paratyphoid fever.
48
What does it mean to make a diagnosis of typhoid fever clinically?
The combination of a history of being at risk for infection and a gradual onset of fever that increases in severity over several days should raise suspicion of typhoid or paratyphoid fever.
49
How is typhoid fever treated?
- Antimicrobial therapy - Fluoroquinolone (most commonly ciprofloxacin) - Injectable third-generation cephalosporins - Treatment with an appropriate antibiotic.
50
How does antimicrobial therapy treat typhoid fever?
Specific antimicrobial therapy shortens the clinical course of typhoid fever and reduces the risk for death.
51
Whats the problem with treating with fluoroquinolone?
resistance to fluoroquinolones is highest in the Indian subcontinent and increasing in other areas.
52
What class of treatment are fluoroquinolones?
Empiric treatment
53
When are Injectable third-generation cephalosporins used?
Injectable third-generation cephalosporins are often the empiric drug of choice when the possibility of fluoroquinolone resistance is high.
54
How does an appropriate antibiotic treat typhoid fever?
the height of the fever decreases each day.
55
How long will it take for a patient treated with appropriate antibiotics to defervesce completely?
3-5 days.
56
How may the patient feel while on the antibiotic treatment?
Patients may actually feel worse during the time that the fever is starting to go away.
57
What should be done if the fever does not subside within 5 days of antibiotic treatment?
If fever does not subside within 5 days, alternative antimicrobial agents or other foci of infection should be considered.
58
What does the CDC recommend to travellors for typhoid fever?
CDC recommends typhoid vaccine for travellers to areas where there is a recognized increased risk of exposure to S. Typhi.
59
What are the drawbacks of the typhoid vaccine?
- The typhoid vaccines currently available do not offer protection against S. Paratyphi infection. - Travelers should be reminded that typhoid immunization is not 100% effective, and typhoid fever could still occur.
60
What are the two vaccines available in the US?
- Oral live - Vi capsular polysaccharide vaccine (ViCPS).
61
What percentage of people do the two US vaccines protect?
Both vaccines protect 50%–80% of recipients.
62
How is the ViCPS vaccine administered?
Intramuscularly.
63
How long before exposure should the ViCPS vaccine be given?
One dose of this vaccine should be given at least 2 weeks before expected exposure.
64
What system was used to review typhoid fever?
SES staff then reviewed the typhoid fever cases reported through the notifiable disease surveillance system and characterized the cases by person, place, and time (i.e., performed the descriptive epidemiology).
65
What did Hypothesis-generating interviews reveal was in common in the 10 studied patients of typhoid fever?
all of the patients had purchased groceries from state- approved markets. However, four of the patients had also purchased food from local street vendors, with fruits and vegetables being the most commonly purchased items. The households of all patients included in hypothesis-generating interviews were supplied with public water.
65
Details about water in the hypothesis-generating interviews?
The households of all patients included in hypothesis-generating interviews were supplied with public water. All but one patient reported that the water was often cloudy and occasionally had a foul smell.
66
What did SES investigators hypothesise caused the typhoid fever outbreak/ what the mode of transmission was as a result of the hypothesis-generating interviews?
SES investigators hypothesised the public water supply as the source of the Dushanbe typhoid fever outbreak. The widespread occurrence of cases throughout the city, affecting both sexes and all age groups, was indicative of a waterborne outbreak. Complaints during the hypothesis-generating interviews about the quality of the public water further heightened their suspicions.
67
How did SES investigators confirm their hypothesis about a waterborne outbreak of typhoid fever?
SES investigators conducted a case-control study to test the hypothesis that the public water system was the source of the typhoid fever outbreak in Dushanbe.
68
How was a case defined in the case-control study?
a case was defined as an illness in a person that included the following: Clinical criteria: - sustained fever (oral temp >= 38.5degC) - one or more other signs and symptoms indicative of typhoid fever (e.g., weakness, stomach pains, headache, loss of appetite, or rose-coloured rash) - culture of stool or blood positive for Salmonella Typhi. Restrictions of time, place, and person: - onset of symptoms after February 1, - resident of Dushanbe, and - person with earliest onset of symptoms in household.
69
Define clinical criteria.
criteria to be classed as a case.
70
How were case patients interviewed?
interviewed within 5 days of hospital admission by a trained SES interviewer, using a standardized questionnaire. Questions focused on exposures during the 30 days before onset of illness
71
What was infection with S. Typhi associated with?
- associated with drinking water that had not been boiled during the 30 days before onset of symptoms. The odds ratio increased with the amount of water consumed each day. - Obtaining water from a tap outside the home and eating food obtained from street vendors were also associated with illness.
72
What was seen to be a protective factor against s. typhi?
Using boiled water in the home and eating butter, apples, or onions were determined to be protective factors.
73
What was not associated with illness?
Factors not associated with illness included type of toilet facilities; drinking beverages with ice; eating or drinking at restaurants or a friend’s or relative’s home; traveling outside Dushanbe or receiving visitors who usually reside outside Dushanbe; and consuming raw fruits and vegetables (other than apples and onions), dairy products (other than butter), and medicines.
74
What did SES do to confirm their suspicions about contaminated water?
Evaluated Dushanbe public water supply. Viewed maps of watersheds for the treatment plants. Toured all water treatment plants. Investigators observed treating procedures at each plants. Inspected equipment used.
75
How many water treatment plants did Dushanbe have?
Dushanbe had four water treatment plants
76
What water did the treatment plants use?
used surface and groundwater.
77
What water did the two treatment plants in the north part of the city use?
surface water
78
What water did the two treatment plants in the south part of the city use?
groundwater
79
Give some examples of ground water.
water from underground
80
Give some examples of surface water.
Rivers, lakes, ponds
81
Why is surface water generally contaminated in Dushanbe?
Lack of wastewater purification facilities or storage in villages and factories along the river resulted in the discharge of communal wastes directly into the river.
82
How was surface water treated in northern Dushanbe?
1) water was strained and held in open sedimentation basins where particulates were allowed to settle out naturally. 2) Chlorine was added directly to the sedimentation basins before the water was passed through sand filters to allow for adequate contact time. 3) From the filters, water was pumped into the distribution system without further storage.
83
How was ground water treated in southern Dushanbe?
The water for the two groundwater treatment plants (i.e., Kafernigan and South-West Stations) was pumped directly from the wells into holding tanks and from the holding tanks into the public water distribution system without treatment.
84
What are the usual steps in treating a public water supply to make it safe to drink?
Filtration, chemicals (chlorine), UV treatment.
85
What was wrong with the surface water treatment stations in the north that caused contamination of the water, causing typhoid fever?
- sedimentation basins were filled with silt and algae. - Dredging machines used to remove the silt were broken. - Sand filters had formed mud balls and displayed substantial fouling with iron-oxide that can compromise the filtration process. - water at treatment stations not chlorinated regularly since December
86
Whats a mud ball?
conglomerations of filter material that form if a filter is not cleaned adequately.
87
What was wrong with the ground water treatment stations in the south?
Inspections of the groundwater treatment stations were unrevealing. - Wells in good condition. - Wellhead seals functioning correctly. However, approximately half of the pumps at these stations were not operational, limiting the ability to provide the city with adequate water pressure. Plant workers had scavenged spare parts to maintain the functionality of the remaining pumps.
88
How did SES investigators test the water at each of the 4 treatment plants?
SES investigators tested treated water samples from each of the water treatment plants for turbidity and fecal coliforms.
89
What is turbidity?
amount of suspended particles in a solution.
90
What is the unit of measure for turbidity?
Unit : NTU : nephelometric turbidity units
91
Q1. Out of these measures, which one is the most likely to prevent typhoid fever? a) Washing vegetables before consumption b) Boiling drinking water c) Avoiding eating butter d) Avoiding social contact
b
92
What is the method used for drawing phylogenic trees ?
Comparing DNA or RNA sequences
93
What were the results of the tests on water samples?
The turbidity of treated water from the Napornaya Station was 150 nephelometric turbidity units (NTUs). Faecal coliforms were 132 colony forming units (CFU)/100 mL. Treated water from the Samotechnaya Station had a turbidity of 70 NTUs; fecal coliforms were 118 CFU/100 mL. Both groundwater plants pumped faecal-coliform-free water with a turbidity of 0 NTUs.
94
Why did surface water and ground water blend?
Water leaving all four water treatment plants entered an interconnected distribution system where surface and groundwater blended
95
Why did SES investigators measure water hardness?
To distinguish the source of water supplied to different parts of the city, SES investigators measured water hardness at the treatment plants and at a sample of consumer taps.
96
What water source did northern Dushanbe receive its water from according to the SES investigators?
They determined that the northern part of the city received water primarily from the surface water treatment plants
97
What water source did southern Dushanbe receive its water from according to the SES investigators?
The southern part of the city received water primarily from the groundwater treatment plants.
98
What water source did the central part of Dushanbe receive its water from according to the SES investigators?
The central part of the city received water from both the surface and the ground water treatment plants.
99
How would you collect a water sample from a water tap for faecal coliform testing?
- Test for turbidity - Microscope.
100
What was in the water that caused typhoid fever?
faecal coliforms.

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