In the past, malaria killed two out of three missionaries in certain locales. Depending on the prevalence of disease, the missionary must decide on how many layers of protection are needed. Strategies include sleeping under an insecticide-treated net, avoiding outside at dawn and dusk, screening windows and doors, wearing mosquito repellent, reducing mosquito breeding sites, taking malaria prophylactic medication, and evaluating and treating every fever within 24 hours of onset. The decision about which strategies to employ should be made in consultation with medical providers with knowledge of local patterns of disease. Diagnosis may be affected by presence of prophylactic medications, test kits that only detect certain species, or variable experience of lab personnel. Recurrent malaria may be due to reinfection, recrudesence, or relapse, and diagnosis and treatment requires knowledge of disease patterns related to P. vivax and P. ovale. Testing will often be negative and disease may occur weeks to years after leaving the malarious area, making treatment more difficult, especially if the missionary is back in his/her passport country.