CIE AS LEVEL Biology: Infectious
disease Questions with Complete
Solutions.
What is a disease - Answer A disease is an illness or disorder of the body or mind that leads
to poor health.Each disease is associated with a set of signs and symptoms
What is an infectious disease - Answer Infectious diseases are caused by pathogens and are
transmissible (can be spread between individuals within a population) e.g cholera, malaria,
HIV/AIDS and tuberculosis
What are non infectious diseases - Answer They are diseases that aren't caused by a
pathogen and we transmissible e.g chronic obstructive pulinwry disease, lung cancer, sickle cell
anaemia and cystic fibrosis.
Causative agents(pathogens) and the type of organism that cause infectious diseases - Answer
Cholera: Vibrio Chlora (pathogen)- bacterium
Malaria: Plasmodium falciparum, Plasmodium malaria, Plasmodium vivax, Plasmodium ovale-
Protoctist
Tuberculosis : Mycobacterium Tuberculosis, Mycobacterium Bovis - bacterium
HIV/AIDS : human immunodeficiency virus - virus
Transmission of cholera - Answer Cholera is caused by the bacterium Vibrio choleraeThe
disease is water-borne (the bacterium lives in water) and food-borneThis means the disease
occurs where people do not have access to proper sanitation (clean water supply) and
uncontaminated foodCholera can be transmitted when people; bath or wash in contaminated
water, drink contaminated water, or eat food exposed to contaminated waterInfected people
egest large numbers of the bacteria in their faecesIf these faeces contaminate the water supply,
or if infected people handle food or cooking utensils without washing their hands, then the
bacteria are transmitted to uninfected people
Transmission of malaria - Answer Malaria is caused by one of four species of the protoctist
PlasmodiumThese protoctists are transmitted to humans by an insect vector:Female Anopheles
mosquitoes feed on human blood to obtain the protein they need to develop their eggsIf the
person they bite is infected with Plasmodium, the mosquito will take up some of the pathogen
with the blood mealWhen feeding on the next human, Plasmodium pass from the mosquito to
the new human's blood
Malaria may also be transmitted during blood transfusion and when unsterile needles are re-
usedPlasmodium can also pass from mother to child across the placenta
, Transmission of tuberculosis - Answer When infected people with the active form of the
disease cough or sneeze, the Mycobacterium tuberculosis bacteria enter the air in tiny droplets
of liquidTB is transmitted when uninfected people then inhale these dropletsTB therefore
spreads more quickly among people living in overcrowded conditionsThe form of TB caused by
Mycobacterium bovis occurs in cattle but is spread to humans through contaminated meat and
unpasteurised milkVery few people in developed countries now acquire TB in this way, although
meat and milk can still be a source of infection in some developing countries
Transmission of HIV/AIDS - Answer Human Immunodeficiency Virus is a retrovirusThe HIV
virus is not transmitted by a vector (unlike in malaria)The virus is unable to survive outside of
the human bodyThe virus is spread by intimate human contact and can only be transmitted by
direct exchange of body fluidsThis means HIV can be transmitted in the following ways:sexual
intercourse
blood donation
sharing of needles used by intravenous drug users
from mother to child across the placenta
mixing of blood between mother and child during birth
from mother to child through breast milk
Prevention and control of cholera - Answer Cholera occurs when people do not have access
to effective sanitation facilities and access to clean waterIt is difficult to prevent and control
cholera because of:The fast-growing cities in developing countries not having the appropriate
infrastructure. They have limited funds for large-scale projects such as the provision of drainage
systems, sewage treatment facilities and clean water suppliesHumanitarian crises (eg.
displacement of people due to wars or natural disasters), which can cause the destruction of
sanitation infrastructure and/or the provision of poor sanitation facilities in overcrowded
temporary housingThe use of raw human sewage to irrigate crops
Prevention of cholera can occur through:Providing adequate sewage treatment
infrastructureThe provision of clean, piped water that has been chlorinated to kill bacteria (as
this occurs in developed countries, cholera is very rare among them)vaccination programmes in
areas where cholera is endemic
Cholera can be controlled by:Ready access to treatments such as oral rehydration therapy (a
solution containing glucose, salts and water)Monitoring programmes by the World Health
Organisation (WHO)Using antibiotics in severe cases (to reduce the risk of antibiotic resistance)
Prevention and control of malaria - Answer The 3 main methods for reducing malaria
are:Reducing the number of Anopheles mosquitoes in an area,Reducing the chance of being
bitten by these mosquitoes,Using drugs to prevent Plasmodium infecting humans
As Anopheles mosquitoes (specifically female mosquitoes) are the vectors that transmit
Plasmodium between human hosts, the transmission cycle of malaria can be broken (or at least
reduced) by reducing the number of these mosquitoes. This can be achieved by:Spraying living
disease Questions with Complete
Solutions.
What is a disease - Answer A disease is an illness or disorder of the body or mind that leads
to poor health.Each disease is associated with a set of signs and symptoms
What is an infectious disease - Answer Infectious diseases are caused by pathogens and are
transmissible (can be spread between individuals within a population) e.g cholera, malaria,
HIV/AIDS and tuberculosis
What are non infectious diseases - Answer They are diseases that aren't caused by a
pathogen and we transmissible e.g chronic obstructive pulinwry disease, lung cancer, sickle cell
anaemia and cystic fibrosis.
Causative agents(pathogens) and the type of organism that cause infectious diseases - Answer
Cholera: Vibrio Chlora (pathogen)- bacterium
Malaria: Plasmodium falciparum, Plasmodium malaria, Plasmodium vivax, Plasmodium ovale-
Protoctist
Tuberculosis : Mycobacterium Tuberculosis, Mycobacterium Bovis - bacterium
HIV/AIDS : human immunodeficiency virus - virus
Transmission of cholera - Answer Cholera is caused by the bacterium Vibrio choleraeThe
disease is water-borne (the bacterium lives in water) and food-borneThis means the disease
occurs where people do not have access to proper sanitation (clean water supply) and
uncontaminated foodCholera can be transmitted when people; bath or wash in contaminated
water, drink contaminated water, or eat food exposed to contaminated waterInfected people
egest large numbers of the bacteria in their faecesIf these faeces contaminate the water supply,
or if infected people handle food or cooking utensils without washing their hands, then the
bacteria are transmitted to uninfected people
Transmission of malaria - Answer Malaria is caused by one of four species of the protoctist
PlasmodiumThese protoctists are transmitted to humans by an insect vector:Female Anopheles
mosquitoes feed on human blood to obtain the protein they need to develop their eggsIf the
person they bite is infected with Plasmodium, the mosquito will take up some of the pathogen
with the blood mealWhen feeding on the next human, Plasmodium pass from the mosquito to
the new human's blood
Malaria may also be transmitted during blood transfusion and when unsterile needles are re-
usedPlasmodium can also pass from mother to child across the placenta
, Transmission of tuberculosis - Answer When infected people with the active form of the
disease cough or sneeze, the Mycobacterium tuberculosis bacteria enter the air in tiny droplets
of liquidTB is transmitted when uninfected people then inhale these dropletsTB therefore
spreads more quickly among people living in overcrowded conditionsThe form of TB caused by
Mycobacterium bovis occurs in cattle but is spread to humans through contaminated meat and
unpasteurised milkVery few people in developed countries now acquire TB in this way, although
meat and milk can still be a source of infection in some developing countries
Transmission of HIV/AIDS - Answer Human Immunodeficiency Virus is a retrovirusThe HIV
virus is not transmitted by a vector (unlike in malaria)The virus is unable to survive outside of
the human bodyThe virus is spread by intimate human contact and can only be transmitted by
direct exchange of body fluidsThis means HIV can be transmitted in the following ways:sexual
intercourse
blood donation
sharing of needles used by intravenous drug users
from mother to child across the placenta
mixing of blood between mother and child during birth
from mother to child through breast milk
Prevention and control of cholera - Answer Cholera occurs when people do not have access
to effective sanitation facilities and access to clean waterIt is difficult to prevent and control
cholera because of:The fast-growing cities in developing countries not having the appropriate
infrastructure. They have limited funds for large-scale projects such as the provision of drainage
systems, sewage treatment facilities and clean water suppliesHumanitarian crises (eg.
displacement of people due to wars or natural disasters), which can cause the destruction of
sanitation infrastructure and/or the provision of poor sanitation facilities in overcrowded
temporary housingThe use of raw human sewage to irrigate crops
Prevention of cholera can occur through:Providing adequate sewage treatment
infrastructureThe provision of clean, piped water that has been chlorinated to kill bacteria (as
this occurs in developed countries, cholera is very rare among them)vaccination programmes in
areas where cholera is endemic
Cholera can be controlled by:Ready access to treatments such as oral rehydration therapy (a
solution containing glucose, salts and water)Monitoring programmes by the World Health
Organisation (WHO)Using antibiotics in severe cases (to reduce the risk of antibiotic resistance)
Prevention and control of malaria - Answer The 3 main methods for reducing malaria
are:Reducing the number of Anopheles mosquitoes in an area,Reducing the chance of being
bitten by these mosquitoes,Using drugs to prevent Plasmodium infecting humans
As Anopheles mosquitoes (specifically female mosquitoes) are the vectors that transmit
Plasmodium between human hosts, the transmission cycle of malaria can be broken (or at least
reduced) by reducing the number of these mosquitoes. This can be achieved by:Spraying living
