Preventing infections

25 min

Defences you see every day

Look around a Rwandan village or town and you can see a whole system built to stop infections: a treated mosquito net over every bed, a handwashing point at the entrance to a shop or school, a community health worker (umujyanama w'ubuzima) testing a child for malaria at home, and babies queuing at the health centre on vaccination day. Each of these breaks a link in the chain of infection you studied in lesson 3. In this lesson you will match each defence to the link it breaks, using malaria as the main example.

Definition

Prevention: action taken to stop an infection happening at all. Example: sleeping under a treated net.

Vaccination: giving a vaccine (a harmless form or part of a pathogen) so that the body learns to fight that pathogen before meeting it.

Insecticide-treated net (ITN): a mosquito net treated with an insecticide, which both blocks and kills mosquitoes that land on it.

Indoor residual spraying (IRS): spraying the inside walls of houses with an insecticide that kills mosquitoes resting there.

Malaria: follow the cycle, then break it

Figure 1: The malaria transmission cycle. Malaria is caused by the protoctist Plasmodium and carried by female Anopheles mosquitoes; green labels show where the cycle can be broken.

Only the female Anopheles mosquito spreads malaria, because only females feed on blood (they need it to make eggs), and they bite mostly at night. The parasite needs both hosts: it must pass from person to mosquito and back to a person. Breaking the cycle at any stage protects the whole community.

A mother and her child under an insecticide-treated bed net (Rufiji District, Tanzania). A net only works if it is used every night, has no holes and is tucked under the mattress. Photo: President's Malaria Initiative, US Government, public domain, via Wikimedia Commons

Worked example 1: which link does each measure break?

Use Figure 1 to explain how each measure interrupts malaria: (a) a treated bed net; (b) indoor residual spraying; (c) filling in puddles and clearing blocked drains during umuganda; (d) a community health worker testing and treating a feverish child the same day.

(a) The net stops the mosquito biting at night, blocking stages 1 and 4 (the mode of transmission), and the insecticide kills mosquitoes that land on it.
(b) Spraying kills mosquitoes resting on walls, so fewer survive the 10 to 14 days the parasite needs in stage 5.
(c) Mosquitoes lay eggs in stagnant water; removing it means fewer new mosquitoes (fewer vectors).
(d) Treatment kills the parasites in the child's blood (stage 3), so the child recovers and there are no parasites for a mosquito to pick up at stage 4: the reservoir is removed.

How Rwanda prevents infections

Community health workers. Every village elects its community health workers (abajyanama b'ubuzima). In August 2018, after umuganda, villages across the country elected a fourth one, so there are now four per village. They test and treat malaria and diarrhoea in the community, give advice on nutrition and hygiene, and follow up pregnant women (Ministry of Health, 2018).
Bed nets and spraying. The government gives insecticide-treated nets to the whole population in a national campaign about once every three years (the last before 2026 was in 2023); between campaigns, nets go to pregnant women and babies under one year. Houses in selected districts are also sprayed (Ministry of Health and RBC, reported January 2026).
Vaccination. Between 2009 and 2013 Rwanda added vaccines against pneumococcus, rotavirus, measles and rubella, and the human papillomavirus (HPV), reaching more than 90% of the target children for each. In 2011 Rwanda became the first African country to run a national HPV vaccination programme, starting in schools, to protect girls against cervical cancer.
Handwashing stations. Before Rwanda confirmed its first case of COVID-19 in March 2020, handwashing stations were set up at the Kigali bus park, and handwashing points like the one in the photo below soon became a common sight at the doors of shops, schools and offices.
Mutuelle de santé (lesson 1) makes testing and treatment affordable, so infections are treated early and spread less.

What you can do

Measure	Link it breaks	Diseases it helps prevent
Wash hands with soap and water after the toilet and before eating or cooking, rubbing the palms, backs, between the fingers and under the nails	mode of transmission	cholera, typhoid, dysentery, colds, influenza
Use a latrine; keep it clean and covered	portal of exit	cholera, typhoid, bilharzia, worms
Drink boiled or treated water; cover food	mode of transmission	cholera, typhoid, hepatitis A
Sleep under a treated net every night	mode of transmission (vector)	malaria
Cover coughs and sneezes; open windows	portal of exit; mode of transmission	tuberculosis, influenza, COVID-19
Complete all vaccinations	susceptible host	measles, polio, tuberculosis (BCG), HPV and others
Never share needles, razors or toothbrushes	mode of transmission (body fluids)	HIV, hepatitis B
Eat a balanced diet; sleep well	susceptible host (a stronger body resists infection)	many infections
Get tested and treated early; finish the medicine	reservoir	malaria, tuberculosis, and others

Worked example 2: net coverage in a village

A community health worker surveys 150 households (illustrative figures). 120 have a treated net over every sleeping place; 30 do not. (a) What percentage are fully covered? (b) Why should the 30 households matter to the other 120?

(a) $\frac{120}{150} \times 100\% = 80\%$ .
(b) People in the 30 uncovered households are bitten more, so more of them become infected. Each infected person is a reservoir: mosquitoes that bite them pick up parasites (stage 4) and can then infect people anywhere in the village, including people whose nets were torn or who sat outside in the evening.

Conclusion: prevention protects the whole community, not just the family that uses it; that is why the health worker follows up the remaining 20%.

Warning

Common mistakes. (1) "A bed net is only for children." Everyone who sleeps where malaria occurs should use one. (2) "Once I feel better I can stop the medicine." Stopping early can leave pathogens alive and helps them become resistant; finish the whole course. (3) "Water that looks clear is safe." Pathogens are too small to see; boil or treat drinking water. (4) "Vaccines are only for babies." Some, such as HPV, are given to older children.

The loathsome, lethal mosquito (TED-Ed). Watch for why only female mosquitoes bite, how they carry diseases such as malaria from one person to another, and why controlling them matters.

Tip

Exam technique. For "suggest how to prevent" a disease, always (1) name the route, (2) name the link you are breaking, and (3) give a practical measure. "Malaria is spread by a vector; sleeping under a treated net breaks the mode of transmission by stopping the mosquito biting."

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Practice: preventing infections

Name the pathogen that causes malaria and the vector that carries it.
Why do only female Anopheles mosquitoes spread malaria?
Describe the malaria cycle in four or five steps, starting with a bite.
State two ways in which community health workers help to prevent or control infections in Rwanda.
Which link of the chain of infection does vaccination break? Explain.
In a school of 480 students, 432 have received all their vaccinations. What percentage is this?
Explain why draining stagnant water reduces malaria but does not help against tuberculosis.
A family has one net for five people and two beds. Evaluate their protection and suggest what they should do.

Show answersHide answers

Plasmodium, a protoctist; the female Anopheles mosquito.
Only females feed on blood (they need it to produce eggs), so only they pick up and inject the parasites.
An infected mosquito bites a person and injects parasites; the parasites multiply in the liver; they enter red blood cells, multiply and burst them, causing fever; another mosquito sucks up parasites when it bites; the parasites develop in the mosquito and move to its salivary glands, ready for the next bite.
Any two: they test and treat malaria and diarrhoea in the village; they teach hygiene and nutrition; they follow up pregnant women; they help with vaccination campaigns and bed net distribution.
The susceptible host: the vaccinated person's body is prepared to fight the pathogen, so they are no longer easily infected.
$\frac{432}{480} \times 100\% = 90\%$ .
Mosquitoes breed in stagnant water, so removing it reduces the vectors of malaria. Tuberculosis spreads through the air from coughs and has no vector, so stagnant water has nothing to do with it.
Poorly protected: people sleeping outside the one net can be bitten and infected, and they then act as a reservoir for the whole family. They should get a net for every sleeping place (from the health centre or community health worker), use them every night and tuck them in.

Key points

Malaria is caused by Plasmodium and spread by female Anopheles mosquitoes; the parasite passes between people and mosquitoes.
Nets, spraying, draining stagnant water and early testing and treatment each break a different part of the cycle.
Rwanda's defences include community health workers in every village, national bed-net campaigns, vaccination, handwashing stations and Mutuelle de santé.
Personal hygiene, safe water, latrines and completing vaccinations prevent many infections.

1Defences you see every day

2Malaria: follow the cycle, then break it

3How Rwanda prevents infections

4What you can do

Defences you see every day

Malaria: follow the cycle, then break it

How Rwanda prevents infections

What you can do