Ugandan authorities declared an outbreak of Ebola last month after 54 people were infected with the virus.

At least 19 people have died, including four health workers since September 20. The first case in the capital, Kampala, was recorded last week.

Ugandan authorities have documented more than 1,100 contacts of known Ebola patients, according to the Africa Centres for Disease Control and Prevention. The Sudan strain of Ebola, for which there is no proven vaccine, is circulating in the country of 45 million people.

Ugandan President Yoweri Museveni on Saturday imposed a 21-day travel lockdown on two Ebola-hit districts – Mubende and Kassanda – as part of efforts to stop the spread of the contagious disease.

World Health Organization (WHO) chief Tedros Adhanom Ghebreyesus said last week that clinical trials of two vaccines could begin in the coming weeks pending Ugandan government approvals, without naming the vaccines.

At least six vaccines are in development for the Sudan strain, including three that have progressed to phase-one clinical trials, according to the WHO.

Ebola, which manifests as a viral haemorrhagic fever, is spread through contact with bodily fluids of an infected person or contaminated materials. Symptoms include fever, vomiting, diarrhoea, muscle pain and at times, internal and external bleeding.

Ebola first appeared in 1976 in two simultaneous outbreaks in South Sudan and the Democratic Republic of the Congo, where it occurred in a village near the Ebola River after which the disease is named.