PII S0736-4679(02)00457-2 Clinical Communications MALARIA: A RISING INCIDENCE IN THE UNITED STATES David A. Jerrard, MD, Joshua S. Broder, MD, Jeahan R. Hanna, MD, James E. Colletti, MD, Katherine A. Grundmann, MD, Adam J. Geroff, MD, and Amal Mattu, MD University of Maryland School of Medicine, Baltimore, Maryland Reprint Address: David Jerrard, MD, 27 Brett Manor Court, Hunt Valley, MD 21030 e Abstract—Malaria is frequently a deadly disease, par- ticularly in tropical countries of the world where this pro- tozoan infection is endemic. While physicians in tropical countries are familiar with the presentation, those who do not practice in endemic regions of the world may neglect to add tropical diseases to their differential diagnosis of fever. Epidemiologic data from the CDC show the number of cases of malaria being diagnosed in the United States in the last decade has risen sharply. With international travel continuing to rise, there is strong reason to consider ma- laria as a source of fever. © 2002 Elsevier Science Inc. e Keywords—malaria; pathophysiology; emerging resis- tance; diagnostic tests; chloroquine INTRODUCTION Malaria is a mosquito-borne, protozoan infection that primarily affects red blood cells. The symptoms that result resemble many more common illnesses. Fever, malaise, myalgias, headache, and vomiting are a few of the usual findings that fail to distinguish this disease from numerous others. Unfortunately, particularly with certain species of malaria, death may result. Other prom- inent sequelae may include thrombocytopenia, severe anemia, renal failure, jaundice, hepatosplenomegaly, convulsions, and coma. The vast majority of the world’s new cases and deaths due to malaria occur in sub-Saharan Africa. The concen- tration of poverty, political instability, and constant mi- gration of non-immune refugees into endemic malarial areas has done much to drive these numbers (1). In addition to these factors, sub-Saharan Africa and other areas of the world such as Southeast Asia and South America have seen emergence of resistance to formerly very effective medications by various species of Plasmo- dium. The prompt diagnosis of malaria requires that it be included in the differential diagnosis of illness in a fe- brile person with recent history of travel to an endemic area. Clinicians should ask febrile patients for a travel history, particularly when evaluating fever in interna- tional visitors, refugees, migrant laborers, and interna- tional travelers (2). Patients should be asked if they were born overseas, if they have traveled outside of the United States in the last 3 years, or if they have experienced prolonged residence abroad. PATHOPHYSIOLOGY The clinical features, epidemiology, and pharmacologic efficacy of malaria infection are intimately related to the complex lifecycle of the Plasmodium parasites. Human infection begins when sporozoites in the sal- ivary glands of a female Anopheles mosquito are inoc- ulated into the human host as the insect feeds. These parasites rapidly infect human hepatocytes, entering liver cells within 30 min of entering the human body (3). There, each sporozoite divides and differentiates to form up to 30,000 merozoites, which rupture the hepatocyte and enter the blood stream to infect erythrocytes (4). RECEIVED: 13 July 2001; FINAL SUBMISSION RECEIVED: 3 December 2001; ACCEPTED: 8 January 2002 The Journal of Emergency Medicine, Vol. 23, No. 1, pp. 23–33, 2002 Copyright © 2002 Elsevier Science Inc. Printed in the USA. All rights reserved 0736-4679/02 $–see front matter 23