UK GCSE level age ~14-16, ~US grades 9-10 Biology revision notes re-edit 16/05/2023 [SEARCH]

 Communicable diseases: 8. Human immunodeficiency virus (HIV) and the Human papillomavirus (HPV) pathogens

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(8) Examples of viral pathogen communicable diseases

(8a) Human immunodeficiency virus (HIV) a sexually transmitted disease/infection (STD/STI)

HIV is a virus spread by sexual contact or by exchanging bodily fluids like blood e.g. when two people share the same needle in drug taking or sexual intercourse - semen and vaginal fluids.

(A sexually transmitted infection/disease can be defined as an infection/disease that is transmitted via body fluids through sexual contact.)

(HIV is described as sexually transmitted infection/disease, STI/STD)

(An STI can be caused by a bacteria, fungus, protist or virus)

The HIV virus attacks white blood cells, an important part of the body's defence system of the blood.

It reduces the number of lymphocytes, a type of white blood cell that helps your immune system fight infections such as pathogens like viruses and bacteria and reduces the ability to produce antibodies.

For more details see The body's mechanisms of fighting infections

Usually, initially, the HIV infected person experiences flue-like symptoms for a few weeks but then no other symptoms may be experienced for several years. Some people never exhibit flue-like symptoms.

The virus enters the lymph nodes and attacks some of the white blood cells of the immune system.

Antiretroviral drugs are prescribed to inhibit the virus from entering the lymph node tissues which are rich in lymphocytes - essential component of the body's immune system.

If treatment with antiretroviral drugs is not successful, the virus enters the lymph nodes and attacks the body's immune cells.

If diagnosed in time, HIV can be controlled with antiretroviral drugs that stop the HIV virus replicating in the body.

The HIV virus attacks some of the types of white blood cells, kills them and so damaging part of the bodies immune system.

This means the body's defences against other infections, the immune system, is severely weakened and may not be able to cope, including an increased risk of cancer.

AIDS sufferers are also much more susceptible to other communicable diseases like colds and flue and human papilloma virus (HPV).

At this advanced stage, when your body is struggling to cope with any infection at all, HIV leads to 'late stage HIV infection' known as Acquired Immune Deficiency Syndrome (AIDS).

Since HIV prevents the immune system from working properly, the body is extremely vulnerable to infection from any other pathogen - an unfortunate 'knock on' effect because the person's immune system further deteriorates and eventually fails to fight off an infection - an extremely dangerous situation.

e.g. the bacteria that cause the communicable disease would normally be destroyed by the body's immune system before symptoms develop.

However, the immune system of someone infected with the HIV virus are much more likely to display symptoms of tuberculosis and the disease may develop very rapidly - recovery is much more difficult and the outcome can be serious e.g. persistent coughing and lung damage and possibly death.

Prevention of infection and minimising the spread of HIV and hence AIDS

HIV is spread by exchanging infected bodily fluids in sexual intercourse or sharing needles when taking drugs e.g. HIV is transported in blood, semen and vaginal fluids.

So prevention measures to minimise the spread of HIV disease include ...

(i) Using a condom during sexual intercourse

(ii) Drug users NOT sharing needles, infections can be passed on from contaminated needles.

(iii) There are some medications (antiretroviral drugs) available to reduce the risk of passing on the infection during sex - this also applies to mothers passing on the infection to babies during pregnancy.

(iv) Being screened and following up with suitable treatment e.g. antiretroviral drugs which stop the virus reproducing.


(8b) Human papillomavirus (HPV) is a virus that can infect the human reproductive system.

A sexually transmitted infection/disease can be defined as an infection/disease that is transmitted via body fluids through sexual contact (STI/STD)]

The HPV virus is transmitted in bodily fluids, usually during sexual activity.

Infection by the HPV virus doesn't always show symptoms and usually clears up on its own in a couple of months.

Unfortunately, sometimes the HPV infection promotes cell DNA changes causing the formation of certain types of cancer.

It is thought that most cases of cervical cancer arise from HPV infections - one disease causes another.

In this case of a communicable disease (HPV) causes the formation of a non-communicable disease (cancer).


See also Viruses - structure, reproduction and cell destruction


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