An 86-year-old man was the first registered death from the virus in Tunisia, Tozeur regional health director, Yassine Sabri, told local radio Mosaique.
Mr Sabri said authorities are investigating the death of a child to determine if it was caused by the virus.
According to the World Health Organisation, the West Nile virus can cause a neurological disease in humans and could lead to death. It is mainly transmitted to people through the bites of infected mosquitoes.
Symptoms include fever, headache, tiredness, body aches, nausea and vomiting, it also occasional causes skin rash and swollen lymph glands.
The West Nile virus may also cause encephalitis, an inflammation of the brain, or meningitis, an inflammation of the lining of the brain and spinal cord.
Tunisian authorities said that tests were conducted to determine the existence of the West Nile virus in Tozeur after several meningitis cases.
“Health authorities conducted epidemiological and environmental examinations on the cases and carried out the necessary laboratory tests,” the Tunisian Ministry of Health said on Tuesday.
“We also conducted complementary tests, the results of which revealed five confirmed cases of infection with the virus and one death was recorded,” the ministry said.
In recent weeks, locals in Tozeur started noticing an increase of meningitis cases in the governorate, which coincided with an increase in the number of mosquitoes.
A local health worker, who did not wish to be named, told The National that at least five people had died in recent weeks, other than the case confirmed by authorities, after presenting with similar symptoms to those caused by the West Nile virus.
“Authorities have tried to keep this subject under the rug for a while, however, since summer we have been receiving cases of people having high fevers that would not drop even after administering the necessary medication,” the same source told The National.
There is currently no antidote or human vaccine for the virus, only symptom management treatment.
The gravity of the symptoms vary depending on the infected person's immune system.
Locals have shared accounts of family members and friends suffering from the symptoms, and criticised authorities' late response to complaints that an unknown disease might be causing these symptoms.
The Tozeur regional health directorate said they are carrying out a wide-scale disinfection programme and clearing mosquito nests because the disease is transmitted to humans through mosquito bites.