Kagunga, Tanzania - It was a gamble any mother would have made. Jobless, Vanessa Nyitsagama was already struggling to feed her two children, but then news of an outbreak of violence came.

Killings had started in Burundi's capital Bujumbura after protests opposing President Pierre Nkurunziza's decision to run for a third term in office were met with a heavy-handed state-security response.

Where Nyitsagama lived in Nyanza, a town close to the eastern shore of Lake Tanganyika, police were becoming edgy. Armed with Kalashnikovs they manned roadblocks, wanting to see papers and sometimes to solicit bribes.

Nyitsagama's gamble was to leave home with nothing but her children and walk across the border into northwestern Tanzania, a far larger and more stable country. That way, Nyitsagama reasoned, she might secure a better life for them.

With five-year-old Dinase at her side and her infant strapped to her back, she set off on foot, hugging the lake shore until she made it across the border into the usually sleepy fishing village of Kagunga in Tanzania.

Nyitsagama's gamble did not pay off, however.

Mass exodus

About 50,000 other Burundians had similar ideas, and on arrival in isolated Kagunga they found there was nowhere to go.

Nyitsagama and her two children waited for nearly two weeks to get off the beach. With the lake to the west and steep mountains to the south and east, unless fit enough for a gruelling hike, boat is the only option out.

By early May, Kagunga beach was lined, scores deep, with thousands of refugees. A week later, waterborne illnesses tore through the camp. Many were suffering from diarrhoea that soon became suspected cholera cases. The United Nations refugee agency (UNHCR) raced to get the stranded people out of there.

"Everyone is worried about cholera because the place is so congested, as you can see anything can happen," said a harried UNHCR official on the beach.

The UNHCR's best option for evacuating the refugees was to hire the biggest passenger vessel on the lake: the MV Liemba, a former WWI German warship and the vessel that inspired CS Forester's novel The African Queen.

The ship makes two return trips from the Tanzanian port town of Kigoma every day - in the morning and evening - carrying 600 refugees each time. Staff on the boat snatch a few hours sleep when they can.

Young men in white plastic aprons wait on the dock in Kigoma, and when the 67-metre-long Liemba arrives and refugees disembark, they move in with buckets of diluted bleach to strip the decks of disease.

Securing passage

Priority to board the ship is given first to those who are ill. After night fell last Monday, Nyitsagama's daughter Dinase became feverish. Nyitsagama carried her to the small, temporary health clinic where she was given fluids and antibiotics intravenously. They boarded the Liemba the next morning.

Burundi refugees flee to neighbouring Tanzania

Dinase was given a berth in one of the second class cabins, a bag of fluid strung up above, feeding into a vein.

The Liemba is said to be the oldest passenger ship in regular service in the world. Originally christened the Graf von Götzen after the then-governor of German East Africa, she was built in a German shipyard in 1913, and was first used to defend Lake Tanganyika from British and Belgian troops during WWI.

In 1916, she was scuttled by her German captain after being bombed by Belgian warplanes. Then in 1921, Winston Churchill, as First Lord of the Admiralty, ordered her to be dredged and refloated. Rechristened the Liemba after the local name for Lake Tanganyika, she sailed again in 1927.

Few original features remain. The brass plaques denoting first and second class cabins are in English and Kiswahili, the official languages of Tanzania. Much of the refit is Danish, said Captain Benjamin Titus, who has skippered the vessel for 23 years.

But the steel hull is 100 percent original, he said with obvious pride.

"She's still incredibly stable," said the captain. With Titus at the helm, the Liemba has carried refugees before, but on happier occasions - repatriating them to their homeland.

Dying on board

This latest chapter in the ship's century of service is harrowing, Titus said.

Three-quarters of the way through the three-hour journey to Kigoma, Dinase's breathing became laboured. Medical staff from the International Rescue Committee tried to help, but could do nothing. The girl stopped breathing and died.

Dr Hawa Ogumba, working for the International Rescue Committee, stood on deck shortly afterwards, preparing for her second eight-hour shift of the day.

"There are so many people and we're not enough," Ogumba told Al Jazeera. "The evening is the most difficult. Travelling at night, you don't sleep, people are very sick."

Loading the boat from the beach in Kagunga is a complex operation, particularly at night. There is no jetty so the refugees and their belongings must be ferried out in batches by fishermen in deep-hulled wooden boats with two-stroke engines.

From the elderly to the infirm, everyone gets hauled up into the bowels of the Liemba by the crew. The whole process takes hours.

Among those boarding in the early hours of May 19 was Audette Bigirimana, 22. She came from Kabonga, a few kilometres north of the Tanzanian border. In her arms was a featherlight bundle of cloth with her two-day-old baby inside.

Her first child was born in Kagunga, where more than 30 people have now died of cholera, according to the World Health Organization.

As the Liemba sounded its horn and made a starboard turn to dock in Kigoma at 5:30am the next day, Bigirimana and her newborn child slept soundly in the same bunk bed that Dinase had died in hours earlier.

As the vessel's cargo was unloaded, which included the body of one young child, the crew began preparations to depart again.

Refugees continue to arrive in Kagunga by the dozens each day, and the shore is lined with thousands of people waiting to get a place on the ship. For the century-old German former warship and its tireless crew, there is no end in sight.