A-LevelBiologyInfectious diseases9700/21 · May/June 2022 · Q59 Marks

Infectious diseases are caused by pathogens and are described as transmissible diseases.

(a)Explain what is meant by the term transmissible.[1]
(b)Vibrio cholerae is the bacterium that causes cholera. Fig. 5.1 is a transmission electron micrograph of V. cholerae. A student wanted to know the actual length of the flagellum shown in Fig. 5.1. State the information that is needed so that the student can calculate the actual length of the flagellum.[2]
(c)(i)Complete Table 5.1 by calculating the case-fatality rate for Yemen. Table 5.1 country number of cases of cholera number of deaths from cholera case-fatality rate /% Cameroon 1307 55 4.2 DR Congo 29087 501 1.7 Haiti 684 3 0.4 Kenya 5150 39 0.8 Somalia 9968 50 0.5 Sudan 346 11 3.2 Yemen 2260495 3767[1]
(c)(ii)Suggest why large outbreaks of cholera occurred in the countries listed in Table 5.1, but there were very few cases in most other countries.[5]

This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.

Mark scheme

Marking points from the official mark scheme (May/June 2022). The mark or mark type is shown in brackets.

[1] (pathogen / causative organism is) transferred / passed on / AW, (from infected) to an uninfected, person / organism ; I disease I from one person to another unqualified I spread
[2] any two from
[2] information needed
[2] 1 magnification of, image / (electron) micrograph/Fig. 5.1; A scale bar I magnification of (electron) microscope
[2] 2 length of flagellum (in, image / Fig. 5.1); I width / diameter / size
[2] 3 formula actual length of flagellum = measured length of flagellum divided by magnification; A A= 1/M or magnification triangle
[1] 0.2
[5] large outbreaks of cholera in countries shown in Table 5.1 accept ora
[5] any five from:
[5] I ref. to poverty, unqualified
[5] 1 civil disturbance / (civil) war ;
[5] 2 named natural disaster; I famine / drought
[5] 3 lack of, uncontaminated / AW, drinking water ; A examples e.g. no piped water supply / no bottled water / no water treatment
[5] 4 ref. to sewage, qualified ; e.g. no sewage treatment A examples e.g. no separation of drainage from homes and water supplies / contamination of water supplies with human faeces
[5] 5 poor sanitation ; credit only if mp3 or mp4 are not awarded
[5] 6 ref. to poor personal hygiene / described example ;
[5] 7 eating contaminated foods ; e.g. crops irrigated with contaminated water / seafood harvested from contaminated seawater
[5] 8 slow(er) / no / little, diagnosis ;
[5] 9 slow(er) / no / little, treatment / healthcare / medical facilities ;
[5] 10 oral rehydration, (salts / therapy), not, provided / available ; A named example of oral rehydration
[5] 11 antibiotics not, provided / available;
[5] 12 vaccine not provided / vaccine not available / reluctance to be vaccinated / ref to anti-vaccination campaigns ;
[5] 13 poor, understanding of/education about, prevention / treatment / precautions ;
[5] 14 AVP; e.g. difficult to reach people living in, rural / remote / dangerous, areas lack of trained professionals antibiotic resistance ref. to people bringing in cholera from elsewhere