Malaria Surveillance

CENTER FOR DISEASE CONTROL ANNUAL SUMMARY 1973 Issued August 1974 MALARIA SURVEILLANCE TABLE OF CONTENTS I. S U M M A R Y II. T ER M IN O LO G Y III. GENERAL SURVEILLAN^^^PRMATION IV. MILITARY MALARIA IMPORT V. CIVILIAN MALARIA IM P ^ K > FROM ABROAD/ VI. MALARIA ACQUIRED IN VII. MALARIA DEATHS IN TlfclNITED STAjtfS VIII. REPORT FROM THE N A '^^A L MALARIA REPOSITORY, IX. ADDENDUM I X. A D D E N D U M II PREFACE This report summarizes information received from State Health Departments, Medical Departments of the Armed Forces, and other pertinent sources. It is intended primarily for the use of those with responsibility for disease control activities. Anyone desiring to quote this report should contact the original investigator for confirmation and interpretation. Contributions to the Surveillance Report are most welcome. Please address them to: Center for Disease Control Attn: Malaria Surveillance, Parasitic Diseases and Veterinary Public Health Service Bureau of Epidemiology Atlanta, Georgia 30333 SUGGESTED CITATION Center for Disease Control: Malaria Surveillance, Annual Summary 1973 Issued August 1974 Center for Disease Control ........................................................ David J. Sencer, M.D., Director Bureau of Epidemiology ................................................... Philip S. Brachman, M.D., Director Parasitic Diseases and Veterinary Public Health Division ....................................... Myron G. Schultz, D.V.M., M.D., Director Malaria Surveillance......................................................................James J. Gibson, M.D.* Richard E. Brodsky, M.D. Collaborators Bureau of Laboratories General Parasitology Branch, Parasitology Division........................ George R. Healy, Ph.D., Chief National Malaria Repository ............................................. Neva N. Gleason, M.S., Supervisor Margaret Welch, M.T. (ASCP) Fluorescent Antibody Laboratory ............................................. Alex J. Sulzer, Ph.D., Chief Marianna Wilson, B.S., M.S. Computer Systems Branch .................................................................. Charles P. Tyson Through June 30, 1974 I. SUMMARY In 1973, 216 cases of malaria were reported in the United States. This represents a 64.8% decrease, compared with the 614 cases reported for a similar period in 1972. This decline was due almost entirely to decreasing numbers of military cases imported from Vietnam. In 1973, only 41 cases (19% of all cases reported in the United States) were reported among military personnel, and only 31 (14.3% of all cases) were acquired in Vietnam; the smallest number since 1960. As in previous years imported Plasmodium vivax infections were more common than £. falciparum (53.2% versus 21.3%). There were 175 civilian cases of malaria reported in 1973, compared with 160 cases for 1972. In 2 cases, infection was acquired in the United States, in 1 by blood transfusion, and in 1 by congenital transmission. There were 4 malaria deaths reported in 1973 compared with 1 in 1972. All 4 deaths occurred in civilians infected with JP. falciparum malaria. The P. falciparum malaria case fatality ratio of 8.6% was significantly greater than the mean fatality rate for the 10-year period 1963 to 1972 (1.4%). II. TERMINOLOGY The terminology used in this report is derived from the recommendations of the World Health Organization (.1,2). The definitions of the following terms are included for reference purposes. 1. Autochthonous a. Indigenous - malaria acquired by mosquito transmission in an area where malaria is a regular occurrence. b. Introduced - malaria acquired by mosquito transmission from an imported case in an area where malaria is not a regular occurrence. 2. Imported Malaria acquired outside of a specific area (the United States and Puerto Rico in this report). 3. Induced Malaria acquired through artificial means, i.e., blood transfusion, common syringes, or malariotherapy. 4. Relapsing Renewal of clinical activity occurring after an interval from the primary attack greater than that due merely to periodicity. 5. Cryptic An isolated case of malaria not associated with secondary cases as determined through appropriate epidemiological investigation. DHEW Publication No. (CDC) 75-8259 III. GENERAL SURVEILLANCE Between January 1, 1973, and June 1, 1974, 216 cases* of malaria with onset of illness In 1973 in the United States and Puerto Rico were reported to the Parasitic Diseases and Veterinary Public Health Division, Center for Disease Control; this represents a 64.8% decrease with respect to a similar period in 1972 when 614 cases were reported. In addition to the 216 first attacks, reports were also received on 12 individuals who developed 1 or more relapses of malaria caused by the same species as their first attack. The decrease in reported cases was due principally to the decrease of malaria in military personnel (including recently discharged veterans). Military cases declined from 454 in 1972 to 41 in 1973 and comprised 19% of all cases diagnosed in this country (Table 1), compared with 73.9% in 1972. Of the 41 military cases, 31 were acquired in Vietnam. Despite the increasing frequency of international travel, reports of malaria in civilians have remained quite constant over the past 9 years (Figure 1). For 1973, 175 cases of malaria were reported in civilians. Table 1 Military and Civilian Malaria Cases United States, 1959-1973* Year Military Civilian Total 1959 12 38 50 1960 21 41 62 1961 45 37 82 1962 75 40 115 1963 58 90 148 1964 52 119 171 1965 51 105 156 1966** 621 143 764 1967** 2699 158 2857 1968** 2567 130 2697 1969** 3914 145 4059 1970** 4096 151 4247 1971** 2975 205 3180 1972** 454 160 614 1973 41 175 216 *Onset of illness in the United States and Puerto Rico **Figures for these years have been updated to include cases reported after the publication of previous annual summaries. *A "case" is defined as an individuals' first attack of malaria in the United States, regardless of whether or not he had experienced previous attacks of malaria while outside the country. A subsequent attack in the same individual caused by a different Plasmodium species is counted as an additional case. Repeat attacks in this country caused by the same species are considered relapses, not additional cases. All cases included in this report were diagnosed as malaria on the basis of a positive peripheral blood smear examined in a local or state laboratory. Doubtful cases were referred to the National Malaria Repository, CDC 2 Figure 1 MILITARY AND CIVILIAN CASES OF MALARIA, UNITED STATES, 1959-1973 CASES In 1973, in 2 of the 175 civilian cases and in none of the military cases, the patients acquired their infections in the United States. One case was transmitted by blood transfusion, and 1 case was a result of congenital transmission. Both of the cases acquired within the United states were caused by P_. vivax. There was a significant change in the ratios of the cases caused by the various Plasmodium species between 1972 and 1973. In 1973, _P. vivax accounted for 53.2% of infections, a 23% decrease from 1972. This decrease was due to the decrease of malaria in military personnel returning from Southeast Asia which accounted for the majority of £. vivax infections in 1972. P. falciparum was diagnosed in 21.3% of infections (Table 2), and represented a 9.5% increase over 1972. The frequency of infection with J?. malarlae and _P. ovale increased in 1973. Of the 6 mixed infections, 3 were caused by coexistent P^. vivax and £. falciparum. 3 Table 2 Malaria Cases by Plasmodium Species United States, 1973 Species Total Percent P. vivax 115 53.2 P. falciparum 46 21.3 P. malariae 17 7.9 P. ovale 14 6.5 Mixed Infections 6 2.8 Undetermined 18 8.3 TOTAL 216 100.0 The country in which the 216 patients contracted malaria in 1973 is shown in Table 3. Vietnam was listed as the source of 32 imported cases; 31 of these cases were in military personnel. Vietnam returnees, therefore, accounted for 14.4% of all malaria cases in 1973, a marked decrease when compared with 1972 when they comprised 71.8% of all malaria cases. Aside from Vietnam, the largest number of cases were imported from Nigeria (18), Mexico (16), India (16), Pakistan (15)»and Ghana (12). In 1973, only 79 cases (36.6%) acquired infection in Asia, compared with 479 cases (78%) in 1972. This decrease in cases reported from Asia was again due to the decrease in malaria in military personnel returning from Southeast Asia. A history of previous malaria while abroad was obtained in 71 of the 216 imported cases (32.9%) in which this information was available. Patients with £. malariae malaria were more likely to give a history of having had malaria previously (42.9%) than patients with either P. vivax malaria (39.3%) or those with P. falciparum malaria (32.5%). The geographic distribution of the 1973 malaria cases in the United States are shown by the state in which the patient first developed clinical symptoms of the disease (Figure 2). The seasonal distribution of malaria cases has shown no distinct pattern in recent years»and no distinct trend was present in 1973 (Figure 3). As in previous years, clinical malaria developed within 30 days of arrival in the United States in 81.0% of P^. falciparum and in 37.3% of £. vivax infections for which both the exact date of arrival and the date of onset are known (Table 4). This fact is of particular importance because Vietnam veterans are commonly given 1 month’s leave or are discharged from military service as soon as they return home. As a result, they are more likely to be seen by a civilian physician who is seldom as familiar with malaria as the military or Veterans Administration physician. Within 6 months after returning to the country, 97.6 of patients with P^. falciparum malaria and 71.6 of those with ]?. vivax malaria developed clinical symptoms. Only 15 patients with vivax malaria (14.7%) became ill more than 1 year after their last possible exposure to malaria abroad.

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