Symptoms and Signs of Malaria The incubation period is usually 12 to 17 days for P vivax 9 to 14 days for P falciparum 16 to 18 days or longer for P ovale About 1 month (18 to 40 days) or longer (years) for P malariae However, some strains of P vivax in temperate climates may not cause clinical illness for months to > 1 year after infection.