QUESTION

How does the virus cause the symptoms?

ANSWER

Malaria is actually not caused by a virus—it is caused by a microscopic single-celled parasite called Plasmodium. Several different species cause malaria in humans, the most common of which are P. vivax and P. falciparum.

To describe the process in a very oversimplified way, the malaria parasites cause disease by infecting red blood cells, multiplying inside them, then simultaneously bursting out again, destroying then red blood cell in the process. The sudden destruction of lots of red blood cells, plus the debris and waste products left behind by the malaria parasites, stimulate a rapid immune reaction, which itself causes the rapid spike of fever. The characteristic cycles of fever sometimes seen with malaria sufferers occurs because the malaria parasites synchronise their emergence from the red blood cells. The destruction of red blood cells, together with concurrent physiological changes associated with immune response and inflammation, can also lead to decreased haemoglobin levels and anaemia.

More severe clinical symptoms are often seen with P. falciparum malaria infection, particularly if not promptly diagnosed and treated. This is because the P. falciparum parasite infects a red blood cell, it changes the surface of the cell and makes it “sticky”; when the red blood cell then tries to pass through the small blood vessels that lead into the body’s organs, it becomes stuck. This process is known as “sequestration”. If enough red blood cells become sequestered in the organs, it can reduce blood flow to the organ, resulting in oxygen deprivation. When this happens in the blood vessels in the brain, the patient may experience impaired consciousness, confusion and even coma and death—this manifestation is known as “cerebral malaria.”