10.1. Infectious diseases
A subsection of Biology, 9700, through 10. Infectious diseases
Listing 10 of 208 questions
Cholera bacteria release the toxin, choleragen, when they are in the intestine. Name the bacterium that is the pathogen of cholera. Describe the way in which cholera is transmitted from an infected person to an uninfected person. Gangliosides are glycolipids that bind choleragen. These glycolipids are found on many cell surface membranes. When choleragen is released from the bacteria in the intestine, it binds to gangliosides on epithelial cells and enters these cells as shown in . intestinal epithelial cell ganglioside choleragen pathogen not drawn to scale Suggest how choleragen interacts with gangliosides on intestinal epithelial cells. Name the process by which choleragen enters the intestinal epithelial cell as shown in . Once inside the cells choleragen is activated. One effect is to increase the movement of chloride ions through channel proteins out of cells. Suggest and explain the likely consequences on the intestinal epithelial cells of the loss of chloride ions through the channel proteins. Health authorities recommend that antibiotics, such as tetracycline, are only to be used for treating people with severe cases of cholera. Explain why it is recommended that antibiotics should not be given to people with mild cases of cholera or to protect people from cholera.
9700_s17_qp_21
THEORY
2017
Paper 2, Variant 1
View
Name the causative organism of tuberculosis (TB). shows the number of deaths from TB and the number of new cases of TB from 1925 to 2010 in Canada. number per 100 000 population year deaths from TB new cases of TB Key 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 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+ HIV– 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–.
9700_s17_qp_23
THEORY
2017
Paper 2, Variant 3
View
The bacterium Vibrio cholerae is the causative organism of the infectious disease cholera. V. cholerae has structural features typical of all bacterial cells. It also has a flagellum for movement. is an outline drawing of V. cholerae. Complete by drawing and labelling the structures found in V. cholerae. flagellum The World Health Organization (WHO) collects data about cholera from the 194 countries that are members of the World Health Assembly (WHA). In 2015: • there were cases of cholera in 42 of the member countries of the WHA • the total number of cases of cholera reported was 172 454 • there were deaths as a result of cholera in 23 of these countries • the total number of deaths from cholera reported was 1304. The case fatality rate for cholera is the proportion of cases of cholera that results in death within a particular time period. A country with cases of cholera that are properly treated should have a case fatality rate of less than 1%. Calculate the case fatality rate for the 42 member countries of the WHA for 2015. Give your answer to the nearest 0.1%. case fatality rate = % Many of the 23 countries reporting deaths from cholera in 2015 had a case fatality rate of less than 1%. However, two of the 23 countries had case fatality rates greater than 5%. Suggest two explanations for the higher case fatality rate in these two countries. In 2010, the country of Haiti experienced a major earthquake. This led to an outbreak of cholera. Explain why an earthquake may lead to a cholera outbreak. shows data about cholera collected by WHO over a period of 8 years, from 2008 to 2015. These data include: • the total number of cases of cholera for each year • the number of countries in each year that had cases of cholera. 100 000 200 000 300 000 400 000 500 000 600 000 700 000 number of countries number of cases year Key number of cases number of countries Comment on the trends shown in .
9700_s19_qp_22
THEORY
2019
Paper 2, Variant 2
View
Cholera is an infectious disease caused by the bacterium Vibrio cholerae. The pathogen causes disease by disrupting the activity of the epithelial cells in the human intestine. Complete Table 3.1 to compare the structure of V. cholerae and an epithelial cell from the human intestine. Use a tick (3) to indicate the presence of the structure. Use a cross (7) to indicate the absence of the structure. The first row has been completed for you. Table 3.1 cell structure V. cholerae epithelial cell from the human intestine cell wall cell surface membrane ribosomes large permanent vacuole organelles surrounded by a double membrane Describe the methods that can be used to prevent the spread of cholera. The World Health Organization has suggested that people with HIV/AIDS take a longer time to recover from cholera and are at an increased risk of death from cholera. The human immunodeficiency virus (Honly infects certain types of cell. These cells have CD4 receptor proteins in their cell surface membrane. Helper T-lymphocytes have CD4 receptor proteins. is a diagram of HIV showing the glycoprotein gp120. This glycoprotein is embedded in a membrane envelope which surrounds the viral protein coat. gp120 envelope protein coat genetic material The glycoprotein gp120 is important in allowing HIV to only infect certain types of cell. Suggest the role of gp120. People with HIV/AIDS have a low helper T-lymphocyte count. Explain how a low helper T-lymphocyte count could reduce the body’s ability to produce antibodies against V. cholerae.
9700_s19_qp_23
THEORY
2019
Paper 2, Variant 3
View
The Bacillus Calmette-Guérin (BCG) vaccine is the only vaccine used to provide protection against the infectious bacterial disease tuberculosis (TB). Most countries of the world have a BCG vaccination programme. TB is most commonly transmitted from person to person by aerosol infection. The causative organism is present in airborne droplets. Name the species of causative organism of TB commonly passed from person to person by aerosol infection. In general, the countries that do not have a BCG vaccination programme are high-income countries that have a low number of cases of TB. In most of these countries, the vaccine is given only to babies and children at high risk of developing TB. Suggest one reason why a child in a country with a low number of cases of the disease could be at a high risk of developing TB. Countries are classified by the World Bank into one of four income groups. Table 3.1 shows the estimated incidence of TB for 2012 to 2016 for these income groups. The incidence represents the number of new cases of TB occurring per 100 000 people in one year. The new cases include the number of cases that have occurred again after a period of recovery (relapse TB). Table 3.1 incidence per 100 000 people year income group low lower middle upper middle high Describe the patterns and trends shown in Table 3.1. There is evidence that the BCG vaccine has also provided protection against the disease leprosy. Leprosy is caused by a bacterium that is closely related to the bacteria that cause TB. Suggest why the BCG vaccine can also provide protection against leprosy. A baby can gain artificial active immunity to TB after having the BCG vaccine. A baby can also gain natural passive immunity to TB. State the differences between artificial active immunity and natural passive immunity.
9700_s20_qp_22
THEORY
2020
Paper 2, Variant 2
View
In 2016, the highest number of cases of malaria and deaths caused by the disease were in sub‑Saharan Africa. In many areas of sub‑Saharan Africa, malaria is endemic (continually present) and people are at high risk of becoming infected with the Plasmodium pathogen. In high risk areas it is recommended that: • homes are provided with insecticide‑treated nets (ITN) • the surfaces inside homes where Anopheles mosquitoes may rest are sprayed with insecticide. This is known as indoor residual spraying (IRS). Explain how the use of ITN and IRS can help break the transmission cycle of malaria. shows the proportion of the population in sub‑Saharan Africa at risk of malaria that is protected by using IRS or ITN, or both, in the years 2010 to 2016. percentage of population protected year IRS only ITN & IRS ITN only Key The main trend in shows that there is an increase in the percentage of the population protected over time. State one other trend shown in . Explain why the main trend shown in could be a concern for the World Health Organization. With reference to , suggest a reason for the difference in trends shown for ITN only compared with IRS only. In a primary immune response, antibodies against Plasmodium are produced within one to two weeks following infection. In some people, the pathogen is eliminated and the concentration of antibodies in the circulation decreases over time. Infection again by Plasmodium with the same antigens causes a secondary response that also involves antibody production. State and explain how the antibody response following a second infection will differ from the primary immune response. In malaria, the production of antibodies is beneficial to recovery, whereas in the disease myasthenia gravis the production of antibodies is harmful. Explain why the production of antibodies in a person with myasthenia gravis is harmful.
9700_s20_qp_23
THEORY
2020
Paper 2, Variant 3
View
The diseases myasthenia gravis (MG) and HIV/AIDS both involve disorders of the immune system. The cause of MG involves a response by B‑lymphocytes. Explain why MG is called a disorder of the immune system. Studies have indicated that T‑lymphocytes are involved in stimulating the B‑lymphocyte response that causes MG. Research has been carried out on a vaccine that will provide a person with active immunity against these T‑lymphocytes and B‑lymphocytes. Suggest and explain how this vaccine will provide a person with active immunity against the T‑lymphocytes and B‑lymphocytes responsible for causing MG. Many people who are living with HIV (infected with Hdevelop tuberculosis (TB). If a person does not have any symptoms of TB, one preventive measure is to prescribe antibiotics. This reduces the overall number of cases of TB and deaths from TB. State the disadvantage of prescribing antibiotics as a preventive measure against TB. is a summary of some of the statistics published by UNAIDS (Joint United Nations Programme on HIV and AIDS) about HIV and HIV/AIDS for the year 2017. The figures shown in for 2017 are estimated. globally, 36.9 million people were living with HIV 1.8 million people became infected with HIV 940 000 people died from HIV/AIDS 21.7 million were provided with ART (antiretroviral therapy) 35.1 million adults and 1.8 million children (under 15 years) 47% of the people provided with ART, while still living with HIV, do not have detectable levels of the virus in their blood One other statistic published by UNAIDS indicated that, in 2017, only 75% of the estimated 36.9 million people living with HIV knew that they had been infected with the virus. With reference to the information in , discuss the importance of this statistic.
9700_s21_qp_22
THEORY
2021
Paper 2, Variant 2
View
Smallpox, measles and HIV/AIDS are infectious diseases caused by different viruses. These different viruses share some structural features. State one structural feature that would confirm that a pathogen is a virus. The virus that causes smallpox belongs to a different genus to the virus that causes measles. Name the viruses that cause these diseases. smallpox measles Explain why antibiotics, such as penicillin, cannot be used to treat measles. Antibiotics may be prescribed for a person with HIV/AIDS. Suggest why antibiotics may be prescribed for a person with HIV/AIDs. Smallpox is the only infectious disease of humans that has been globally eradicated. This eradication was due mainly to a successful global vaccination programme. Most people who were given the vaccine gained immunity to the disease. A student correctly listed four reasons for the success of the global vaccination programme for smallpox. These reasons are listed in . • The virus did not mutate. • A live virus, closely related to the smallpox virus, was used in the vaccine. • The vaccine was freeze-dried and so was thermostable (heat stable). • The vaccine was easy to administer , so little training was required. Discuss how the reasons listed in contributed to the success of the eradication of smallpox. Table 2.1 lists four types of immunity. Complete each row of Table 2.1 with a tick (3) or a cross (✗) to summarise the types of immunity gained by a person who received the smallpox vaccine. Table 2.1 type of immunity gained (3) not gained (✗) active immunity artificial immunity natural immunity passive immunity
9700_s21_qp_23
THEORY
2021
Paper 2, Variant 3
View
Questions Discovered
208