Pathogens are microorganisms that cause infectious diseases.
Viruses cannot be killed by antibodies
The first symptom of measles is often a fever
After around 3 days a patient with measles will develop a red skin rash.
The measles virus is spread in droplets when an infected person coughs or sneezes.
The virus measles passes into a different person when the droplets in the air and inhaled.
In some cases, complications can develop when a person has measles. These can cause damage to the breathing system and the brain.
In severe cases, measles can be fatal.
Most children are vaccinated against measle when they are very young.
The first symptom of HIV is often a flu-like illness.
The virus is attacking the cells of the patient's immune system.
Over time, the immune system becomes severely damages by HIV.
At some point, the patient's immune system becomes so badly damages that it cannot fight off other infections that other people could easily deal with.
The damage that HIV does to the immune system is also unable to fight off cancer cells.
When the immune system reaches this highly damaged stage, the patient can now contract other infections such as TB. The patient may also develop cancer.
At this highly damaged stage, the patient is describes as having late-stage HIV or AIDS. Frequently at this stage, the disease if fatal.
Antiretroviral drugs stop the virus, HIV, from multiplying inside the patient so the virus does not damage the patient's immune system anymore.
Patients who take antiretroviral drugs do not go on to develop AIDS and they can lead a normal life expectancy.
Antiretroviral drugs are not a cure for HIV and AIDS. The patient must take these drugs for the rest of their life.
HIV is transmitted through the exchange of fluids between humans.
So HIV can be spread by unprotected sex. It can also be spread when drug users share infected needles.
Blood containing HIV can pass in the needle from one person to another.