One of the many areas of society hit hard by the HIV/AIDS epidemic is agriculture. Many thousands of farmers in sub-Saharan Africa have died of the disease, leading to food insecurity.

On this World AIDS Day, the UN Food and Agriculture Organization is calling for greater investment in agriculture and nutritional policies. Marcela Villarreal is director of the FAO's Gender, Equity and Rural Employment Division.

"In the rural areas, we're seeing that in many countries in sub-Saharan Africa, prevalence rates are equal [to] or even higher than in the urban areas. This, of course, has a very important on the agricultural production, clearly. Because when you have people who are sick you cannot produce. Therefore…you will have definitely much lower agricultural production, less food production, less food availability. And also when you don't produce, you can't sell your food. Therefore you don't have the money to buy your food either," she says.

The FAO estimates some countries could lose as much as 25 percent of the agricultural labor force due to HIV/AIDS. "That of course puts a huge constraint on agricultural production and also on agricultural productivity." It says that means countries would have fewer goods to export and less food for rural areas.

As a result, the FAO is working with agricultural ministries to develop labor saving technologies. Villarreal says, "It is very evident when there are huge labor shortages because people are either sick or caring for the sick or have died naturally or are attending funerals. You need agriculture that will be able to function with much less available labor."