Holtz T H, Kachur S P, MacArthur J R, Roberts J M, Barber A M, Steketee R W, Parise M E
Division of Parasitic Diseases, National Center for Infectious Diseases, USA.
MMWR CDC Surveill Summ. 2001 Dec 7;50(5):1-20.
PROBLEM/CONDITION: Human malaria is caused by one or more of four species of intraerythrocytic protozoa of the genus Plasmodium (i.e., P. falciparum, P. vivax, P. ovale, or P. malariae). The protozoa are transmitted by the bite of an infective female Anopheles species mosquito. The majority of malaria infections in the United States occur among persons who have traveled to areas with endemic transmission. Cases occasionally occur that are acquired through exposure to infected blood products, by congenital transmission, or by local mosquitoborne transmission. Malaria surveillance is conducted to identify episodes of local transmission and to guide prevention recommendations for travelers.
Cases with an onset of symptoms during 1998.
Malaria cases confirmed by blood smear are reported to local and state health departments by health-care providers and laboratory staff members. Case investigations are conducted by local and state health departments, and reports are sent to CDC through the National Malaria Surveillance System (NMSS). This report uses NMSS data.
CDC received reports of 1,227 cases of malaria with onsets of symptoms in 1998, among persons in the United States and its territories. This number represents a decrease of 20.5% from the 1,544 cases reported during 1997. P. falciparum, P. vivax, P. malariae, and P. ovale were identified in 42.8%, 37.8%, 3.5%, and 2.1% of cases, respectively. More than one species was present in seven patients (0.6% of total). The infecting species was not determined in 162 (13.2%) cases. Compared with reported cases in 1997, reported malaria cases acquired in Africa increased by 1.3% (n = 706); those acquired in Asia decreased by 52.1% (n = 239); and those acquired in the Americas decreased by 6.5% (n = 229). Of 636 U.S. civilians who acquired malaria abroad, 126 (19.8%) reportedly had followed a chemoprophylactic drug regimen recommended by CDC for the area to which they had traveled. Five persons became infected in the United States. One case was congenitally acquired; one was acquired by blood transfusion; and three were isolated cases that could not be epidemiologically linked to another case. Four deaths were attributed to malaria.
The 20.5% decrease in malaria cases during 1998 compared with 1997 resulted primarily from decreases in P. vivax cases acquired in Asia among non-U.S. civilians. This decrease could have resulted from local changes in disease transmission, decreased immigration from the region, decreased travel to the region, incomplete reporting from state and local health departments, or increased use of effective antimalarial chemoprophylaxis. In a majority of reported cases, U.S. civilians who acquired infection abroad had not taken an appropriate chemoprophylaxis regimen for the country where they acquired malaria. PUBLIC HEALTH ACTIONS TAKEN: Additional information was obtained from state and local health departments and clinics concerning the four fatal cases and the five infections acquired in the United States. Persons traveling to a malarious area should take a recommended chemoprophylaxis regimen and use personal protection measures to prevent mosquito bites. Any person who has been to a malarious area and subsequently develops fever or influenza-like symptoms should seek medical care immediately; the investigation should include a blood smear for malaria. Malaria infections can be fatal if not diagnosed and treated promptly. Current recommendations concerning prevention and treatment of malaria can be obtained from CDC.
问题/状况：人类疟疾由疟原虫属四种红细胞内原虫中的一种或多种引起（即恶性疟原虫、间日疟原虫、卵形疟原虫或三日疟原虫）。这些原虫通过感染性雌性按蚊叮咬传播。美国的大多数疟疾感染发生在前往疟疾流行地区旅行的人群中。偶尔会出现通过接触感染的血液制品、先天性传播或当地蚊媒传播而获得感染的病例。开展疟疾监测以识别本地传播疫情，并指导针对旅行者的预防建议。
1998年出现症状的病例。
通过血涂片确诊的疟疾病例由医疗服务提供者和实验室工作人员报告给当地和州卫生部门。病例调查由当地和州卫生部门进行，报告通过国家疟疾监测系统（NMSS）发送给疾病预防控制中心（CDC）。本报告使用NMSS数据。
CDC收到1998年美国及其属地居民中出现症状的1227例疟疾病例报告。这一数字比1997年报告的1544例减少了20.5%。在病例中，分别鉴定出恶性疟原虫、间日疟原虫、三日疟原虫和卵形疟原虫的比例为42.8%、37.8%、3.5%和2.1%。7名患者（占总数的0.6%）感染了不止一种疟原虫。162例（13.2%）病例的感染种类未确定。与1997年报告的病例相比，在非洲感染的疟疾病例增加了1.3%（n = 706）；在亚洲感染的病例减少了52.1%（n = 239）；在美洲感染的病例减少了6.5%（n = 229）。在636名在国外感染疟疾的美国平民中，据报告有126人（19.8%）遵循了CDC针对其前往地区推荐的化学预防药物方案。5人在美国感染。1例为先天性感染；1例通过输血感染；3例为孤立病例，在流行病学上无法与其他病例关联。4例死亡归因于疟疾。
与1997年相比，1998年疟疾病例减少20.5%主要是由于非美国平民在亚洲感染的间日疟原虫病例减少。这种减少可能是由于疾病传播的局部变化、该地区移民减少、前往该地区旅行的人数减少、州和地方卫生部门报告不完整或有效抗疟化学预防措施的使用增加。在大多数报告病例中，在国外感染的美国平民未针对其感染疟疾的国家采取适当的化学预防方案。
从州和地方卫生部门及诊所获取了关于4例死亡病例和在美国感染的5例病例的更多信息。前往疟疾流行地区的人员应采取推荐的化学预防方案，并采取个人防护措施防止蚊虫叮咬。任何去过疟疾流行地区且随后出现发热或流感样症状的人应立即就医；调查应包括疟疾病血涂片检查。如果不及时诊断和治疗，疟疾感染可能致命。有关疟疾预防和治疗的当前建议可从CDC获取。
