New York, Aug 26 (IANS): Infectious agents can cause a lot of cancer in Africa and researchers believe they now have a clue to how malaria during pregnancy creates the right conditions for a virus to cause cancer in children.

The researchers wanted to explore why the Epstein-Barr virus causes a type of cancer called Burkitt's lymphoma only in some people and not in all infected by the virus.

Rosemary Rochford from the University of Colorado Cancer Center in the US and her colleagues centered their research in Kisumu, Kenya, a port city of just over 400,000. 

In addition to a near universal rate of infection with the Epstein-Barr virus, Kisumu has an unusually high rate of Burkitt's lymphoma and malaria. 

"Because Burkitt's lymphoma is prevalent in areas with a lot of malaria, we thought maybe it could be associated with malaria infection," Rochford said.

Children born to women who have malaria during pregnancy are more predisposed to develop Burkitt's lymphoma, the researchers noted.

"What we think happens is that the risk for these children begins during pregnancy. Usually for most people, the virus is quiet. You never even know you have it. But when you get malaria, the virus reactivates and infects more cells,” Rochford said.

"When mothers get malaria during pregnancy, these malaria-infected cells shed more virus and infants get infected earlier in life. Because they're infected so early, their immune systems don't manage the virus the way they should,” Rochford explained.

"It's not just the fact of exposure to Epstein-Barr virus, but the timing of it that matters. These kids with prenatal exposure due to the secondary pressure of malaria are the ones with increased risk," Rochford said.

One answer to the challenge of virus-associated cancers in Africa would be better and more prevalent use of vaccines. 

Rochford pointed out that the story of Burkitt's lymphoma is similar to the story of other virus-associated cancers, including cervical cancer caused by the human papilloma virus (HPV) and Kaposi's sarcoma caused by the human herpesvirus 8 (HHV8). 

In fact, in Kisumu, Kaposi's sarcoma is the most common cancer in men and cervical cancer is the most common cancer in adult women.

Unlike in the US, where the cancer risk of viruses is far smaller than the risks associated with tobacco and alcohol, "in some parts of Africa, the majority of cancers are caused by infectious agents," said the study published in the journal Current Opinions in Virology.