81. Topic: Epidemiology of Disease X

Correct Answer: E. 10,000/250,000

Explanation: Prevalence refers to the total number of existing cases of a disease within a population at a specific time. In this scenario, the city has a population of 250,000, and there are 10,000 individuals who currently have disease X. Therefore, the prevalence of disease X is calculated as 10,000 existing cases out of the total population of 250,000 (E). The other options (A, B, C, D) do not accurately reflect the number of current cases of disease X in the population.

82. Topic: Disease-Specific Mortality Rate

Correct Answer: A. 400/250,000

Explanation: The disease-specific mortality rate is calculated by taking the number of deaths due to a specific disease and dividing it by the total population. In this case, there are 400 deaths annually due to disease X in a population of 250,000. Therefore, the disease-specific mortality rate is 400 out of 250,000 (A). The other options (B, C, D, E) either represent incorrect calculations or refer to different measures like incidence or prevalence, which are not applicable in this context.

83. Topic: Population Growth Rate

Correct Answer: B. 600/250,000

Explanation: The rate of increase in a population is calculated by dividing the number of new individuals added to the population by the total population size. In this case, an increase of 600 in a population of 250,000 gives the correct rate as 600/250,000. This ratio accurately reflects the rate of population growth, while the other options represent different rates or calculations.

84. Topic: Incidence of Disease X

Correct Answer: C. 1,000/250,000

Explanation: The incidence of a disease in a population is calculated by dividing the number of new cases of the disease by the total population at risk during a specific time period. In this case, with 1,000 new cases in a population of 250,000, the incidence rate is correctly expressed as 1,000/250,000. This provides the accurate measure of how frequently the disease is occurring within this population.

85. Topic: Crude All-Cause Mortality Rate

Correct Answer: D. 2,500/250,000

Explanation:  The crude all-cause mortality rate is calculated by dividing the number of deaths by the total population and is usually expressed per a certain number of people (e.g., per 1,000 or 100,000). In this case, with 2,500 deaths in a population of 250,000, the rate would indeed be 2,500/250,000. This correctly represents the mortality rate for this population, while the other options either overestimate or underestimate the number of deaths.

86. Topic: Carriers and Disease Presentation

Correct Answer: B. Subclinical

Explanation: Patients infected with an agent but never develop clinical symptoms of the disease are known as subclinical carriers. These individuals harbor the infectious agent and can potentially spread the disease, even though they do not exhibit any symptoms themselves. The other terms refer to different phases or types of disease presentations that do not align with the asymptomatic nature of subclinical carriers.

87. Topic: Vaccines Grown in Embryonated Chicken Eggs

Correct Answer: A. Yellow fever

Explanation: While many vaccines, such as measles, mumps, rubella, and influenza, are grown in embryonated chicken eggs, the yellow fever vaccine is an exception. This vaccine is typically grown in tissue cultures or other mediums, making it different from the others listed. Hence, yellow fever does not belong to the category of vaccines grown in embryonated chicken eggs.

88. Topic: Complications of Untreated Syphilis

Correct Answer: A. Obesity

Explanation: Untreated syphilis can lead to severe complications, including blindness (B), psychosis (C), and cardiovascular disease (D). These complications arise from the systemic effects of the disease as it progresses. Obesity (A), however, is not a complication associated with untreated syphilis, as syphilis does not affect body weight regulation or metabolism in a way that leads to obesity.

89. Topic: Sexually Transmitted Infections in Cameroon

Correct Answer: D. Chlamydia

Explanation: Chlamydia (D) ranks as the number one reported communicable disease in Cameroon among sexually transmitted infections (STIs) It is a common STI caused by the bacterium Chlamydia trachomatis, known for its high prevalence and potential to cause significant reproductive health issues if left untreated. Other STIs like syphilis (A) gonorrhea (B) HIV infection (C) and hepatitis B (E) are also prevalent but chlamydia leads in reported cases.

90. Topic: Medical Ethics and Emergency Care

Correct Answer: C. Making the patient comfortable but not transfusing

Explanation: In situations where a parent refuses a blood transfusion for their child due to religious beliefs, the physician must respect the parent’s decision unless it endangers the child’s life or causes significant harm. While seeking a court order (E) is an option, making the patient comfortable (C) is appropriate in non-life-threatening situations while considering the parents’ wishes. Declaring an emergency and transfusing (A) is not ethical without consent or immediate threat to life.

91. Topic: Statistical Tests in Research

Correct Answer: D. Student’s t-test

Explanation: In this study comparing the effects of drug A and drug B on cognitive performance (measured by a memory test) between two groups (drug A and drug B), the appropriate statistical test is Student’s t-test. This test is used to compare the means of two independent groups to determine if there is a significant difference between them. It is commonly used when the outcome variable (memory test scores in this case) is continuous and normally distributed, which is typical for cognitive test scores. Chi-square test (A): This test is used for categorical data, not continuous variables like memory test scores. exact test (B): This test is used for small sample sizes and categorical data, not continuous variables.Multiple linear regression (C): This test is used to analyze the relationship between multiple independent variables and a dependent variable, not specifically to compare means between two groups.Simple linear regression (E): This test is used to analyze the relationship between one independent variable and a dependent variable, not to compare means between two groups. Therefore, Student’s t-test (D) is the most appropriate choice for comparing the average memory test scores between the two groups of patients taking drug A and drug B.

92. Topic: Infant Mortality Rate

Correct Answer: C. The number of deaths up to the first birthday divided by the total number of live births

Explanation: The infant mortality rate is a crucial indicator of public health and reflects the number of deaths of infants under one year of age per 1,000 live births in a given year. The correct definition corresponds to option C:Option A: This describes the crude mortality rate, which is the number of deaths from all causes divided by the total population.Option B: This refers to the post-neonatal mortality rate, which is the number of deaths occurring after the first 28 days and before the first birthday divided by the number of live births.Option C: This is the correct definition of the infant mortality rate, where the number of deaths up to the first birthday is divided by the total number of live births.Option D: This describes the neonatal mortality rate, which is the number of deaths in the first 28 days of life divided by the number of live births.Option E: This simply refers to the total number of live births and does not relate to the infant mortality rate. Therefore, the correct answer for defining the infant mortality rate is option C, as it directly relates the number of infant deaths to the total number of live births in a given population.

93. Topic: Diagnostic Test Specificity

Correct Answer: E. 0.95

Explanation: Specificity of a diagnostic test refers to its ability to identify individuals without the disease as negative correctly. It is calculated as the proportion of true negative results among all individuals without the disease.

94. Topic: Uses of Epidemiology

Correct Answer: C. It makes a clinical diagnosis of disease

Explanation: Epidemiology is a branch of medicine that studies the patterns, causes, and effects of health and disease conditions in defined populations. Its primary uses include:A. Identifies the factors that cause the disease: Epidemiology investigates the determinants and risk factors associated with diseases to understand their origin.B. Explains how and why diseases and epidemics occur: It seeks to understand the mechanisms and pathways through which diseases spread and become epidemics.C. It makes a clinical diagnosis of disease: This statement is incorrect. Epidemiology does not directly make clinical diagnoses of diseases. Clinical diagnosis involves the evaluation of individual patients based on signs, symptoms, and diagnostic tests by healthcare providers.D. Determines the prognosis of a patient: Epidemiology studies help predict the likely outcome of a disease in a population based on factors such as treatment effectiveness and natural history.E. Evaluates the effectiveness of health programs: It assesses public health interventions and programs to determine their impact on disease prevention and control. Therefore, option C is correct because epidemiology is not involved in the direct clinical diagnosis of individual diseases in patients.

95. Topic: Coefficient of Variation

Correct Answer: C. The coefficient of variation

Explanation: The coefficient of variation (CV) is a statistical measure that expresses the ratio of the standard deviation (SD) to the mean of a dataset. It is used to compare the variability of different datasets relative to their means. Here’s a brief explanation of each option for clarity:A. From the fork: This phrase doesn’t correspond to a known statistical term or measure.B. From the variance: Variance is a measure of the dispersion of a set of data points around their mean.C. The coefficient of variation: This is the correct answer. It is calculated as the ratio of the standard deviation to the mean, expressed as a percentage. It is useful for comparing the variability between datasets with different units or scales.D. From the standard error: Standard error measures the variability of sample means around the population mean.E. From the epidemic curve: An epidemic curve is a visual representation of the onset of cases of a disease over time in an outbreak. Therefore, the coefficient of variation (option C) is the correct term that describes the ratio of the standard deviation of a dataset to its mean, often expressed as a percentage.

96. Topic: Vaccination in Immunocompromised Individuals

Correct Answer: C. Oral polio

Explanation: Oral polio vaccine (OPV) contains live attenuated poliovirus strains, which can pose a risk to individuals with severe immunocompromise, as they may not be able to mount a proper immune response and could potentially develop the disease itself from the vaccine strain. Here’s an explanation for each option:A. Yellow fever: This vaccine is generally safe for individuals with household members who are immunocompromised.B. Hepatitis B: This vaccine is also safe for individuals with household members who are immunocompromised.C. Oral polio (OPV): This is the correct answer. OPV should not be administered to individuals living with household members who have severe immunodeficiency due to the risk of vaccine strain disease.D. Influenza: Inactivated influenza vaccine (injectable) is safe for household contacts of immunocompromised individuals.E. Diphtheria: Diphtheria vaccine (part of DTaP or Tdap) is also safe for household contacts of immunocompromised individuals. Therefore, option C, Oral polio vaccine, is the correct answer because it should not be administered to individuals living in households with high immunocompromise due to the risk of vaccine-related disease in severely immunocompromised individuals.

97. Topic: Vaccination During Pregnancy

Correct Answer: B. Pregnant women at risk of high exposures can receive a live viral vaccine

Explanation: Here’s an explanation of each option: A. Live attenuated vaccines should not be given to pregnant women: This statement is generally true because live attenuated vaccines, such as MMR (measles, mumps, rubella) and varicella (chickenpox), are contraindicated during pregnancy due to theoretical risks to the fetus. B. Pregnant women at risk of high exposures can receive a live viral vaccine: This statement is incorrect. Pregnant women should not receive live viral vaccines due to the potential risk of transmission of the live virus to the fetus. C. There is evidence that inactivated vaccines pose equal risks to the fetus: This statement is generally false. Inactivated vaccines (e.g., influenza, Tdap) are considered safe during pregnancy and do not pose equal risks to the fetus compared to live vaccines. D. There is no evidence that immunoglobulins pose a risk to the fetus: This statement is generally true. Immunoglobulins are antibodies and are not known to pose a significant risk to the fetus when administered to pregnant women.E. None of the responses: This option is not correct in this context because option B is incorrect. Therefore, option B, which states that pregnant women at risk of high exposures can receive a live viral vaccine, is the correct answer because live vaccines are generally contraindicated during pregnancy due to safety concerns for the fetus.

98. Topic: Modes of Transmission of HIV

Correct Answer: C. Aerial

Explanation: Here’s an explanation of each option:A. Sexual: HIV can be transmitted through sexual intercourse, both heterosexual and homosexual, if one partner is infected.B. Percutaneous exposure: This refers to transmission through exposure to infected blood or body fluids, such as through sharing needles or accidental needle stick injuries.C. Aerial: There is no documented evidence of HIV transmission through the air (aerial transmission). HIV cannot survive outside the human body for long periods and cannot be transmitted through casual contact or through the air.D. Mother to child: HIV can be transmitted from an HIV-positive mother to her child during pregnancy, childbirth, or breastfeeding.E. None of the above: This option would be incorrect in this context because option C, aerial transmission, is not a documented mode of HIV transmission. Therefore, the correct answer is C. Aerial, as HIV is not transmitted through the air.

99. Topic: Blood Donation and HIV Prevention

Correct Answer: E. All of the above

Explanation: Here’s an explanation of each option: A. Anyone who has had sexual contact with another man since 1997: This restriction applies because men who have sex with men (MSM) have a higher prevalence of HIV infection compared to the general population.B. Current and past intravenous drug users: Intravenous drug use increases the risk of HIV infection due to needle-sharing practices.C. Individuals with multiple sexual partners: Having multiple sexual partners increases the likelihood of exposure to HIV and other sexually transmitted infections.D. Sexual partners of any of the above groups: Individuals who have sexual contact with people in high-risk groups may also be at higher risk of HIV infection.E. All of the above: To prevent HIV infections through blood donations, blood donation centres typically exclude individuals who fall into these high-risk categories to ensure the safety of the blood supply. Therefore, the correct answer is E. All of the above, as these groups are considered at higher risk of HIV infection and should not donate blood to prevent potential transmission through blood transfusions.

100. Topic: Treatment of Minors for Sexually Transmitted Infections

Correct Answer: D. Without parental consent or without informing the parents

Explanation: In many jurisdictions, minors (individuals under the age of 18) can consent to medical treatment for sexually transmitted infections (STIs) without needing parental consent or notification. This is based on principles of confidentiality and the minor’s right to privacy regarding their sexual health. Here’s why option D is correct:D. Without parental consent or without informing the parents: Minors who seek treatment for STIs, including gonorrhea, are often legally allowed to consent to their own treatment without involving their parents. This confidentiality encourages minors to seek medical care promptly without fear of parental notification, which could deter them from seeking necessary treatment.A. But must have the consent of both parents: This is typically not required for minors seeking treatment for STIs.B. But must inform parents: In many cases, minors are not required to inform their parents about STI treatment.C. With the consent of a parent: This option may apply to minors in some situations but not typically for STI treatment, where confidentiality is crucial.E. Without informing the parents but must inform the court: In most cases, minors do not need to involve the court for STI treatment. Therefore, option D is the correct answer as it reflects standard medical practice and legal provisions that protect minors’ rights to seek confidential medical care for STIs.