The malaria was serious risk. Starting from Africa was one of the major aims of this expedition (direct continent-continent route), but before leaving coast paddler could be infected by mosquitoes. Luckily this risk has gone away.
Today Aleksander is over 15 days on the ocean. Severe malaria is almost exclusively caused by P. falciparum infection, and usually arises 6–14 days after infection. He feels right, no symptoms are observed, so we can say that he is safe now. :)