Simplify the following text for a Grade 5 native English-speaking person.
Original: In humans malaria is caused by P. falciparum , P. malariae , P. ovale , P. vivax and P. knowlesi . P. falciparum is the most common cause of infection and is responsible for about 80 % of all malaria cases , and is also responsible for about 90 % of the deaths from malaria .
Simplified: P. vivax and P. falciparum cause the most malaria in people .