(AP) — Bill Clinton says making sure that HIV-infected children in the developing world are well-fed is crucial in fending off the virus.

Clinton says he saw children in Ethiopia who were so malnourished they couldn’t absorb antiretroviral drugs. The former president, who was in Senegal on the final day of a four-nation African tour, says combating the virus is complicated by the sharp spikes in food and oil prices. He says the world has to re-examine how it produces food.

Clinton’s foundation has negotiated agreements to lower the price of rapid HIV tests and anti-AIDS drugs in the developing world and has collaborated with the Geneva-based UNITAID, a U.N.-backed fund that helps supply low-cost antiretroviral drugs.

He is heading to Mexico City to attend an international AIDS conference that starts Monday.