US Malaria Surveillance June 2005
US Malaria Surveillance June 2005
ABSTRACT & COMMENTARY
By Lin H. Chen, MD
Assistant Clinical Professor, Harvard Medical School, Director, Travel Resource Center, Mt. Auburn Hospital, Cambridge, MA
Dr. Chen reports no consultant, stockholder, speaker’s bureau, research, or other financial relationship with companies having ties to this field of study.
Synopsis: Analysis of malaria cases reported in the United States with onset of symptoms in 2003 showed that the number of cases, fatalities, causative Plasmodium species distribution, and origin of infection were similar to those of recent years. Ten cases were actually acquired locally within the United States. Travelers who were visiting friends and relatives (VFRs) continue to have a high risk.
Source: Eliades MJ, et al. Malaria Surveillance—United States, 2003. MMWR Surveill Summ. 2005;54:25-40.
| Table 1 | ||
| US Resources of Recommendations for Malaria Prophylaxis, Diagnosis, and Treatment. | ||
| Source | Contact information, web site, or telephone | Comment: Use |
| Health Information | Order from
Elsevier: www.us.elsevierhealth.com |
Information on distribution and for International |
| or 1-800-545-2522 | recommendations for prophylaxis | |
| Travel 2005-2006 | ||
| CDC Yellow Book | www.cdc.gov/travel/diseases.htm#malaria | Information on distribution and |
| CDC Traveler’s Health | recommendations forprophylaxis | |
| DPDx (CDC’s Division of Parasitic Diseases) | www.dpd.cdc.gov/dpdx | Diagnosis |
| CDC Malaria Branch | www.cdc.gov/malaria/diagnosis_treatment/treatment.htm | Guidelines on management |
| CDC Malaria Branch | 770-488-7788 (8am-4:30pm EST, Monday-Friday) 770-488-7100 (Emergency Operations Center; after hours) |
Assistance in treatment |
In 2003, 1278 cases of malaria were reported to the CDC, including 7 deaths and 10 autochthonous cases (one transfusion-transmitted case in Texas, one cryptic case in Maryland, and 8 introduced cases in Palm Beach County, Florida). The main reason for travel was found to be visiting friends and relatives (VFR) in 53.9% of patients, followed by tourism in 12.5% and missionary work in 9.2%.
P. falciparum was identified in 53.3%, P. vivax in 22.9%, P. malariae in 3.6%, and P. ovale in 2.6% of cases, and 0.9% were mixed infections. Among the infections acquired in Africa, P. falciparum was the predominant species (83.5%), followed by P. vivax (7%). On the other hand, P. vivax was the predominant species for malaria infections acquired in Asia and the Americas (80.4% and 62.9%, respectively). P. falciparum caused malaria less frequently in these regions (12.0% and 31.5%, respectively).
While the total number of cases decreased 4.4% from 2002 due to a 7.0% decrease in cases acquired in Africa, the number of cases acquired in Asia and in the Americas increased by 3.5% and 4.3%, respectively. The majority of cases (70%) were acquired in Africa, predominantly West Africa. Fifteen percent of cases were acquired in Asia (especially India) and 12.3% in the Americas (primarily Central America and Hispaniola). Three percent of cases were acquired in Oceania.
Twelve percent of all imported malaria cases had onset of illness before arriving in the United States, although the majority of P. falciparum cases (79.4%) developed symptoms within 1 month after arrival. In contrast, 42.2% of P. vivax cases had onset of illness within 1 month after arrival. A greater proportion of P. vivax cases had onset of illness from 1 month to 1 year after arrival in the United States.
Chemoprophylaxis use was assessed in order to determine drug failure and resistance. Nineteen percent of US civilians reported taking a recommended chemoprophylaxis, but only about one-third adhered to the regimen. Blood samples were unavailable, and compliance and parasite resistance could not be determined.
Thirty-one cases of malaria occurred in pregnant women, 18 in US civilians, 12 in foreign civilians, and 1 unspecified. Among the civilian cases, all had traveled to Africa and 78% were VFRs. Pregnant women made up 7% of cases in women, and pregnant women were less likely to be taking chemoprophylaxis compared to nonpregnant women.
Commentary
The slight decrease in malaria cases reported to the CDC from 2002 (1337 cases)1 to 2003 (1278 cases) likely represents cyclical fluctuation, but may indicate lower transmission in some endemic areas, a decline in travel to endemic areas, or possibly improved preventive strategies. Some of these factors would require more detailed surveys, and some may come to light only if the numbers of US travelers to malaria endemic regions were available to be compared with annually reported malaria cases.
Patterns of malaria infections remain consistent with past reports.1 Specifically, P. falciparum continues to be the leading causative species, followed by P. vivax. Most cases were acquired in Africa. P. falciparum caused the majority of cases acquired in Africa, whereas P. vivax was the leading cause in Asia and the Americas. VFR travelers had the highest risk for acquiring malaria. Additional patterns emerged: malaria cases in US civilians increased in recent years, while cases in foreign civilians decreased, suggesting increased travel among US civilians and decreased immigration to the United States. The rise in number of cases acquired in Asia and the Americas may reflect increased travel to these regions, as well as immigration from these regions leading to increased VFR travel. Similarly, the decrease in cases acquired in Africa, although possibly a minor fluctuation, may be associated with a decline in immigration from Africa.
The 18 cases of malaria that occurred in pregnant US civilians raises concern because of severity of malaria during pregnancy, as well as ill effects on the fetus including congenital malaria.2 The majority of the pregnant women in this report traveled for the purpose of visiting friends and relatives, and may have had the misconception that they were immune to malaria. Additionally, pregnant women were less likely than nonpregnant women to take a malaria chemoprophylaxis, indicating inadequate pre-travel advice. Travel medicine specialists should counsel pregnant women to avoid travel to malarious areas, and emphasize the consequences of malaria during pregnancy and possibility of congenital malaria. If travel must occur during pregnancy, detailed education regarding personal protective measures and chemoprophylaxis options should be discussed.
A recent report on malaria deaths in the United States identified failures in various areas,3 which are again illustrated by the 7 fatal cases attributable to malaria reported in 2003:
1. failure to diagnose
2. delay in diagnosis
3. lack of chemoprophylaxis
4. inappropriate chemoprophylaxis
5. inadequate treatment
6. history of travel not elicited
7. failure to seek medical evaluation
In comparison, 8 fatalities attributable to malaria were reported in 2002.1 In order to reduce mortality from malaria, both increased public awareness of malaria and improved education of clinicians are needed. The CDC launched a new malaria web site that contains excellent information for both travelers and clinicians, and has diagnosis and treatment guidelines, available at www.cdc.gov/malaria. Whenever chemoprophylaxis failure is suspected, health care providers should CDC in order to measure drug levels.
Finally, the cases of malaria acquired in the United States show that competent vectors remain. Periodically autochthonous cases have occurred in the United States. In 2002, there were 5 such cases: 1 congenital case, 1 transfusion-transmitted case, 2 cases of locally acquired mosquito-transmitted malaria in Virginia, and 1 cryptic malaria in New Jersey.1 Health care providers should consider malaria in the differential diagnosis of patients with fever of unknown origin.
References
1. Shah S, et al. Malaria Surveillance—United States, 2002. MMWR Surveill Summ. 2004;53(SS01):21-34.
2. CDC. Congenital Malaria—Nassau County, New York, 2004. MMWR Morb Mortal Wkly Rep. 2005;54(15):383-384.
3. Newman RD, et al. Malaria-Related Deaths Among US Travelers, 1963-2001. Ann Intern Med. 2004;141:547-555.
By Lin H. Chen, MD Assistant Clinical Professor, Harvard Medical School, Director, Travel Resource Center, Mt. Auburn Hospital, Cambridge, MA Dr. Chen reports no consultant, stockholder, speakers bureau, research, or other financial relationship with companies having ties to this field of study.Subscribe Now for Access
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