Infectious Diseases
111 questions· page 1 of 12
Complete the flow chart in Fig. 3.1 by identifying:
• the modes of transmission
• the scientific names of the pathogens
• the name of one of the diseases.
HIV has a nucleic acid core of RNA. The virus also contains the enzyme reverse transcriptase.
After HIV enters T-lymphocytes, reverse transcriptase catalyses the formation of DNA using activated DNA nucleotides with the viral RNA as a template.
Some drugs, such as tenofovir, have been developed to inhibit the action of reverse transcriptase.
The structure of tenofovir is similar to the structure of deoxyribose adenosine monophosphate, as shown in Fig. 3.2.
After tenofovir is absorbed into cells it is phosphorylated twice and can be used by reverse transcriptase in the synthesis of DNA.
When a tenofovir molecule is added to the DNA strand being synthesised, the process stops.
Suggest the mechanism of action of tenofovir to prevent the synthesis of DNA by reverse transcriptase. Use the information in Fig. 3.2 in your answer.
Calculate the percentage of people who received PrEP in 2019 as a percentage of the target set by the UN in 2016.
Give your answer to the nearest whole number.
...................................................... %
PrEP does not prevent transmission of HIV.
State and explain how health authorities can reduce the transmission of HIV.
Cholera is caused by a bacterial pathogen.
Name the bacterial pathogen that causes cholera.
Suggest and explain why the people affected by the cyclone were at serious risk of cholera.
Doxycycline is one of the main antibiotics used for the treatment of cholera.
Doxycycline enters the pathogen and binds to one of the subunits of the bacterial ribosome. This prevents growth and reproduction of the bacterial cell.
Suggest and explain how binding of doxycycline to ribosomes stops growth of the bacterial cell.
Penicillin, which used to be prescribed for the treatment of cholera, has a different mechanism of action to doxycycline.
State which part of the bacterial cell is affected by the action of penicillin.
Mozambique was one of the countries badly affected by the cyclone.
As part of the effort to prevent a greater number of cases of cholera from occurring, two different approaches were taken.
• Approximately doses of the oral cholera vaccine were sent to Mozambique and a large-scale vaccination programme was organised.
• Medical centres were set up in Mozambique to treat people with cholera.
Suggest and explain how the two different approaches helped to prevent a greater number of cases of cholera from occurring.
State the most effective antibiotic to treat infections of bacterium X and bacterium Y.
bacterium X ______
bacterium Y ______
Suggest why bacterium Y had a different sensitivity to each of the three antibiotics.
Explain how the use of vaccines in the control of infectious diseases differs from the use of antibiotics.
The presence of the pathogen in the lungs attracts phagocytes to the area of infection. The phagocytes release elastase, which digests elastin.
Many people with TB feel tired all the time.
Suggest and explain how the effect of phagocytes on tissues in the lungs leads to people feeling tired all the time.
Discuss the biological factors and social factors that make TB a difficult disease to control.
Fig. 3.1 shows the number of deaths from TB and the number of new cases of TB from 1925 to 2010 in Canada.
The vaccine for TB was introduced in Canada for widespread use from 1948.
Antibiotics, such as streptomycin, were introduced in Canada from 1940.
Use the information in Fig. 3.1 to comment on the effect of the introduction of the vaccine and antibiotics on the number of new cases and deaths from TB.
In 2010, Swaziland had one of the highest death rates from TB in the world.
Swaziland also had a high number of new cases of HIV infection in its population in 2010.
People who are infected with HIV are described as HIV+ and people who are not infected with HIV are described as HIV–.
Table 3.1 shows the number of deaths from TB in Swaziland in 2010.
Table 3.1
| HIV status | number of deaths from TB per 100,000 population |
|---|---|
| HIV+ | 400 |
| HIV– | 91 |
Using the information in Table 3.1, suggest why the number of deaths per 100,000 population of people who are HIV+ is much higher than that in people who are HIV–.
In 2014, the World Health Organization (WHO) estimated that 3200 million people were at risk of malaria. This was almost half of the world population in 2014.
Table 4.1 shows the number of cases of malaria and the number of deaths from malaria between 1998 and 2013. The table shows numbers for all the countries of the world and for the countries in the WHO African region.
The table also shows the numbers in the African region as percentages of the numbers for all countries.
Table 4.1
| year | number of cases of malaria in millions (all countries) | number of cases of malaria in millions (African region) | cases in the African region as a percentage of all countries | number of deaths from malaria in thousands (all countries) | number of deaths from malaria in thousands (African region) | deaths in the African region as a percentage of all countries |
|---|---|---|---|---|---|---|
| 1998 | 272.9 | 237.6 | 87.1 | 1110.0 | 961.0 | 90.1 |
| 2003 | 236.0 | 186.6 | 79.1 | 872.0 | 800.0 | 91.7 |
| 2008 | 225.1 | 181.0 | 80.4 | 747.0 | 677.0 | 90.6 |
| 2013 | 198.0 | 158.4 | 80.0 | 584.0 | 525.6 | 90.0 |
Describe the trends shown in Table 4.1.
Suggest reasons why the number of cases of malaria and the number of deaths from malaria changed between 1998 and 2013.
Malaria is very difficult to control even though there is improved understanding of the disease.
Explain why malaria is very difficult to control.
Table 1.1 shows features of three infectious diseases: malaria, tuberculosis (TB) and cholera.
Complete Table 1.1.
Table 1.1
| feature | malaria | tuberculosis | cholera |
|---|---|---|---|
| name of pathogen | ________________ falciparum | Mycobacterium tuberculosis | ________________ ________________ |
| type of organism | ________________ | bacterium | ________________ |
| method of transmission | ________________ ________________ ________________ | ________________ ________________ ________________ | drinking water and food contaminated with human faeces |
NQR is an important respiratory enzyme located in the cell surface membrane of the bacterium that causes cholera.
A student suggested that an inhibitor of the enzyme NQR could be used as a drug in the prevention and control of cholera.
Suggest and explain how this inhibitor would function.
Calculate the total cholera fatality rate for 2008.
Show your working.
answer = ______
Apart from differences in total population size in each of the regions, suggest explanations for the differences shown in Table 5.1.