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Vaccines, Blood & Biologics

Traveler's malaria, locally-transmitted malaria, and transfusion-transmitted malaria in the United States

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Traveler's malaria, locally-transmitted malaria, and transfusion-transmitted malaria in the United States

FDA Workshop on Testing for Malarial Infections in Blood Donors
July 12, 2006

Monica E. Parise, MD
Centers for Disease Control and Prevention

The findings and conclusions in this report are those of the author and do not necessarily represent the views of the Centers for Disease Control and Prevention

Malaria in the United States

  • Approximately 1,000-1,500 cases reported annually
    • Imported - 99%
    • Locally acquired (up to about 10 cases/year)

Locally-acquired malaria


  • Induced by blood transfusion or organ transplantation, needle-stick, intravenous drug use, nosocomial transmission (errors)
  • Congenital
  • Local mosquito-borne transmission occasionally occurs.


Local Mosquito-borne Transmission - United States, 1957-2005


Number of malaria cases among U.S. and foreign residents, by year - United States,* 1973-2004


Number of immigrants to the United States, 1820-2003


Rates among U.S. travelers abroad, 1993-2003*


1999 Incidence, by Region

RegionImmigrants, Refugees & Asylees*Travelers*
All Regions33.882.95

* Incidence per 100,000 persons

Incidence of malaria in US travelers, immigrants, refugees, and asylees


Rates calculated using traveler data from World Tourism Organization and figures for immigrants, refugees, and asylees from INS.


Rates calculated using traveler data from World Tourism Organization and figures for immigrants, refugees, and asylees from INS


What about the resorts? Risk is so low. Can't you all just give us those?


  • Risk is in the resorts in rural areas except La Altagracia Province, DR
  • We hear arguments about what is a rural vs urban resort.we have some evidence that there were cases from a resort town that is argued to be big/urban
  • Highlights need for best evidence-based recommendations possible


What about the resorts? (II)

  • These are areas where CDC considers risk high enough to recommend prophylaxis for travelers (although possible will go to standby treatment for very low risk situations in future).would seem risky to not defer blood donors


  • Raises some interesting questions/issues:


    • Base recommendations on the endemic situation (conservative approach) vs traveler (or TTM) data?
    • Given the micro-epidemiology of malaria, if base on traveler data, must remember that assumptions based on the average traveler may not hold for all
    • What would be an acceptable level of risk?

Number of malaria cases, by Plasmodium species - United States, 2002-2004


Trend in Species from 1985-2003


Region of acquisition of malaria cases - United States, 2004


Malaria acquired in Africa, 2003


  • Travel to Africa accounts for only 0.6% of U.S. travel in 2003
  • Yet 66.2% of all malaria infections and 85.9% of all P. falciparum infections were acquired in Africa in 2003
  • From 1985-2002, 93% of all malaria deaths in US travelers due to Pf - 73% of those were acquired in sub-Saharan Africa


Malaria acquired in the Americas, 2004: US surveillance data

Central America154941
South America81710

Species data from the Americas

  • PAHO (2004)


    • Reports P. malariae in Americas - most cases from Guyana and Suriname. Also from Venezuela, Colombia, Belize
    • No mention of P. ovale


  • Review article on P. ovale (Collins WE, 2005)


    • No P. ovale mentioned from Americas

VFR travel

  • Purpose of travel in 44% of the 26 million trips made in 2002 (excluding Canada and Mexico)
  • GeoSentinel: VFR travelers have 8 times higher risk of acquiring malaria than tourists (Leder CID 2004)

VFR = immigrant who returns to homeland to visit friends and relatives

Results: Characteristics of 96 Cases


Characteristics Of 69 Implicated Donors


Implicated Donors

  • For 62 implicated donors where the epidemiologic investigation was complete:


    • 61% should have been excluded if the donor deferral guidelines had been correctly applied
    • 39% would not have been excluded; of these, 2/3 had Plasmodium malariae


Implicated Donors


0.09 cases/million units transfused where guidelines were followed

Prior Residents of Endemic Areas

Persons who return home to visit friends and relatives (n = 8):

  • Correct time limit for donor deferral?
  • Five cases arose within 1 year
  • Two of the others were Pm and > 3 yrs
  • Only one case (Pf at 29 months) would have been prevented with change from 1-year to 3-year exclusion

Malaria Species Involved


* 2 cases were unknown species

Species involved in TTM cases by region, 1963-2005


Implicated donors, by decade


*VFR = Persons who previously lived in an endemic area, now live in the US, and return to their country of origin to visit friends/relatives

Incidence of Transfusion- Transmitted Malaria, 1963-2005


TTM.the last 15 years (1990-2005)

  • 16 cases (donor implicated in 14)


    • 12 - immigrants; two persons born in US but who lived long-term overseas grouped into this category
    • 1 - US traveler (Kenya)
    • 1 - VFR (Africa)


  • 12/14 (86%) acquired in sub-Saharan Africa (2 in China due to Pm)


  • 71% due to Plasmodium falciparum
    21% P. malariae - China; 7% P. ovale


  • Failure of screening process in 71%



  • Low incidence TTM with current guidelines


    • Incidence 0.23 cases/ million units transfused
    • 0.09 cases/ million units transfused where guidelines were followed


  • Highest risk


    • Immigrants
    • Exposure in Africa


  • Sonja Mali
  • Lou Katz
  • Heather Wachtel


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