The West African Ebola outbreak has halted progress in tackling HIV in Sierra Leone, shutting health clinics and scaring patients from being tested or seeking treatment, the United Nations has said.

In an internal document seen by the Thomson Reuters Foundation, the United Nations Development Programme (UNDP) raised concerns that HIV prevalence and drug resistance in the country could increase as a result.

The worst recorded outbreak of Ebola has killed more than 9,500 people, infected over 23,500 others and placed immense pressure on already weak health systems in hardest-hit Sierra Leone, Guinea and Liberia.

"Hospitals have closed down because they have been overrun by Ebola patients and non-Ebola patients are too afraid to go to them for fear of catching the virus," said Hakan Bjorkman, who manages UNDP's AIDS programme.

"HIV prevention activities in schools and awareness raising for the general population has been suspended due to the restriction of movement, the closure of all education institutions and the overall ban on public gathering."

Some 25 percent of patients taking antiretroviral therapy (ART) for the virus that causes AIDS are missing clinic appointments in and around Sierra Leone's capital Freetown, where the main Ebola affected communities are, Bjorkman said.

There has also been a decline of at least 70 percent in HIV testing and counselling services and logistical issues mean that essential HIV drugs are either expiring or quickly becoming out of stock, according to the UNDP document that was released internally in December.

"If this is not dealt with quickly, we risk the virus spreading to more people, more people dying of opportunistic disease like tuberculosis and the virus building up a resistance to our drugs," Bjorkman told the Thomson Reuters Foundation by telephone from Geneva.

Some 58,000 people are living with HIV in Sierra Leone, a country of around 6 million people. About a third of those affected need life-saving ART, however, as of June 2014, only 10,673 people were receiving ART, the report said.

Bjorkman said the Global Fund to Fight AIDS, Tuberculosis and Malaria had provided some $55 million to deal with AIDS in Sierra Leone between 2013 and 2015, but only around $25 million had been spent to date, partly due to the Ebola response.

"We need to kick-start counselling and testing on high risk groups, follow up on patients who have defaulted on their treatment, and restart campaigns in schools and public places now the bans have been lifted," he said.

However, there may be one positive impact of the Ebola outbreak on HIV infection rates in West Africa.

"People are scared of having sex in this time of Ebola, which could have an impact in reducing HIV infection too," said Bjorkman, noting that the Ebola response needs to drum home use of condoms and not just washing hands.