Malaria is an infectious disease. It is caused by parasites. People catch malaria when the parasite enters the blood. The parasite causes a deadly infection that kills many people each year.
The parasite that causes malaria is a protozoan called Plasmodium. Protozoa are organisms with only one cell, but they are not bacteria. Bacteria are smaller and simpler than protozoa.
There are several species (kinds) of Plasmodium that cause malaria in humans.
Dengue fever is a fever. It is caused by a virus which can be spread by mosquitos, similar to Malaria. Symptoms resemble that of a common cold.
The WHO says some 2.5 billion people, two fifths of the world's population, are now at risk from dengue. Estimates are that there may be 50 million cases of dengue infection worldwide each year. The disease is now endemic in more than 100 countries.
Yellow fever is an illness that is caused by a virus. The illness can cause bleeding problems. It is called yellow because the skin sometimes becomes yellow as it does with jaundice.
There is a vaccine that can stop the disease, but many people in Africa and South America are not vaccinated against it.
The World Health Organisation says that 200.000 people are made ill with yellow fever every year and that 30.000 people die from it.
Hepatitis A is viral infection of the liver caused by the hepatitis A virus. Unlike the other common forms of hepatitis (hepatitis B and C) it does not cause chronic liver disease.
Signs and symptoms include:
Nausea and Emesis
Loss of appetite
Hepatitis B is not spread by food or casual contact. Instead, hepatitis B is spread by blood or body fluids from an infected person.
A baby can get it from its mother during childbirth, and it can also be spread by sexual contact, use of street drugs,
and unsafe medical care.
Some people just have hepatitis B for a little while and then suppress the infection, but others can be infected for life usually with few or no symptoms for many years. Hepatitis B sometimes damages the liver severely and can cause cancer.
There is a vaccine that works very well to prevent hepatitis B, and there is a treatment for people with serious diseases caused by hepatitis B.
Influenza, better known as the flu and sometimes called the grippe, is a common childhood illness but is not as common among Adults. It is not limited to humans, most mammals and many birds can also catch influenza. It is caused by several different viruses (see: RNA virus), which is why people can have the flu more than once. The name influenza comes from Italian: influenza, meaning "influence".
Human Influenza can pass from one person to another very easily. It is most commonly spread by the microscopic droplets of mucus and fluid that are sent into the air when the sick person coughs or sneezes. Symptoms include cough, sore throat, muscle aches and pains, fever, headache, and rarely vomiting and diarrhea. Influenza can also lead to other diseases, such as pneumonia. This makes it especially dangerous to young children and old people.
Although there is no cure for influenza, antiviral drugs can be used to treat the illness so it is not as severe and does not last as long.