Hope Siwale, of the Tearfund-supported EFZ Christian charity, said she feared that the shortfall in the Global Fund to treat HIV, tuberculosis and malaria could reverse many of the advances in treating the disease and put additional pressure on governments and churches in developing nations.
The Global Fund is a major provider of anti-retroviral drugs but according to Tearfund, it lacks sufficient funds to continue its current level of work over the next three years. The development agency said that demand for ARVs was outstripping supply and that two in three sufferers around the world were still without access.
Mrs Siwale said the effect of funding shortages at the community level would not be good.
"We have seen positive things and lives changed from people who were on the edge of dying and then living again and becoming productive again and active in the community," she said.
"If funding continues to go down or fall below what is needed means there will be even more pressure on the Zambian government and the church to be there."
Around the world, people are marking World AIDS Day with campaigning and awareness raising on behalf of the 33.3 million living with HIV.
Although the number of new infections and deaths from HIV and AIDS is in general decline worldwide, Mrs Siwale warned that millions of people were still in need of treatment and care.
"For people to get treatment they have to walk maybe 15km and in one area there may be only one mission hospital servicing more than 20,000 people and all of them have to walk long distances to that hospital. The need is still there and the need is still vast," she said.
The church is educating people about treatment, running home-based care programmes, and supporting those who have lost loved ones to HIV and AIDS.
Sometimes children are left to fend for themselves when both their parents have succumbed to the disease. In other instances, widows find themselves unable to take care of the children by themselves and so fall back on their elderly parents.
Mrs Siwale fears a shortfall in funding will only make things harder for families – and the church.
"It is not like one person's problem but it becomes a family problem," she explained.
"With a reduction in funding, these families will fall back on the church and the church doesn't have the means to support all of these families.
"Even the people who are sick in the hospitals are really dependent on the church."
It is also jeopardising progress towards Millennium Development Goal One – universal access to antiretroviral drugs. The MDGs were agreed in 2000 by world leaders but with only five years left on the clock until the target date for their fulfilment, HIV workers and development agency are concerned they will not be met.
Mrs Siwale praised the efforts of the Zambian government – which provides free ARVs to HIV/AIDS sufferers, but urged all world governments to keep their promise to provide universal access to preventative treatment and make every effort to move those HIV/AIDS sufferers who are still on waiting lists into the necessary treatment programmes.
She appealed to people everywhere to support HIV/AIDS sufferers and continue praying for them.
She said: "HIV and AIDS is about life and death. The drug is a lifesaving drug and we should support and encourage people on ARVs and let them know that hope is not lost."