Only two African countries have bone marrow donor registries accredited by the world marrow donor association, Nigeria and South Africa.

只有两个非洲国家的骨髓捐赠者登记得到了世界骨髓捐赠者协会的认可，这两个国家是尼日利亚和南非。

If this is the case, the search is expanded to a database containing the genetic makeup of millions of voluntary bone marrow donors.

这种状况下，搜寻范围就要扩大到包含数百万骨髓捐赠者的基因资料库。