Impact of migration travel and geography

While travel, migration, and trade are expanding rapidly over the globe, the movement between countries of blood components for transfusion is still relatively uncommon, and to date the blood supply of developed nations has remained remarkably immune from infection by travel and migration. For example, it is estimated that 300-500 million people have malaria, but perhaps only a handful of cases each year in the United States are due to infection via the blood supply. Similarly, while Chagas' disease is endemic in Mexico, Central and South America, and millions of people from these countries travel annually to America, the reported incidence of Chagas' disease due to blood transfusion in the United States is very, very low (Chamberland et al., 1998). Nevertheless, concern is real because blood is an extraordinarily effective vehicle for transmitting infectious agents (Chamberland et al., 1998). Since a fully effective laboratory test for every blood-transmissible infectious disease in the world is not on the horizon, the current first line of defense will have to remain effective health screening and public education before individuals give blood. It also is hopeful to note that new laboratory tests to screen human blood are being developed. As noted already, in the wake of improved screening tests for infections transmissible by transfusion, we are seeing a greater emphasis on developing screens for parasites (e.g. Chagas' disease and malaria) that can infect the blood supply. Even with these population shifts, the blood supply in developed nations remains remarkably safe, as illustrated in Table 7.5, which shows the low rate of transfusion-related infection due to malaria and to T. cruzi infections not endemic in the United States, as well as babesiosis, which is endemic in the US.

Table 7.5 Estimates of the risk of infectious complications of blood transfusion: Babesia, malaria, T. cruzi

Agent

Frequency per million units (per actual unit)

Clinical disease

Acute per million units

Chronic per million units

Deaths per million units

Babesia

>1

(>1/100,000)

1.0

0

0.25

Malaria

>4

(>1/250,000)

4.0

0

0.00

T. cruzi

24-80

(1/12,500-1/50,000)

0.0-1.0

0

0.00

Source: Adpated from Dodd (1994).

Source: Adpated from Dodd (1994).

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