Bangladesh's deadliest measles outbreak in decades is stretching its health system, with children filling hospital wards and doctors struggling to contain a surge in infections that have killed more than 300 youngsters.

The South Asian nation had made advancements in vaccinations to help stem the deadly virus -- but coverage gaps during and after the chaos of a 2024 uprising that overthrew the autocratic government left the youngest generation badly exposed.

"I was almost sure I was going to lose her today -- her condition was terrible in the morning," said Rina Begum, 45, cradling her three-year-old granddaughter Afia.

Begum, her eyes red from exhaustion and tears, said Afia had missed her second dose of the measles vaccine at age 18 months, and had spent the last two weeks in the measles ward in Dhaka.

Measles is highly contagious, spreading through coughs and sneezes, and has no specific treatment once caught.

It hits children the hardest. Their breathing can become strained, their strength fades, and in the most severe cases, the infection reaches the brain, causing swelling that can lead to lasting damage -- or death.

Hospitals are treating thousands of young patients while authorities race to expand vaccination coverage and prevent more deaths.

Begum, 45, offered a smile as Afia reached up -- having just turned a corner and regained some strength.

"After putting her on oxygen, now she is doing much better," she said.

Doctor's help

Bangladesh has recorded 336 child deaths since March 15, with more than 50,000 confirmed and suspected cases, according to the latest government data.

Most cases recorded have been among children aged between six months and five years.

On May 4 the country recorded the grim milestone of the highest number of children dying in a single day -- 17 in 24 hours.

Bangladesh has made significant advancements in vaccinations to tackle infectious diseases, but a measles drive due in 2024 was delayed by the revolution that toppled the government of Sheikh Hasina.

Health officials, aided by the UN children's agency, WHO, and the security forces, are working to vaccinate children, launching an emergency measles-rubella campaign on April 5.

Nearly 17 million children have received the vaccine since the drive started, according to government data.

Last year the vaccine coverage was only 59 percent, but 95 percent coverage of children is needed to ensure herd immunity.

Without herd immunity, children can still get infected after vaccination, said senior health ministry official Abu Hussain Md Moinul Ahsan.

It would take around a month before results can be seen, Ahsan added.

Siam, a 14-month-old boy, spent 10 days in intensive care at Dhaka's Shishu Hospital, a children's centre, before improving enough to return to the dedicated measles ward.

He was vaccinated at 10 months, but with wider herd immunity compromised, that was not enough.

"I did not expect to get my son back," said his mother Brishti Akhtar, aged 20, watching her son sleep with an oxygen tube attached to his nose, one of 97 children with measles in the hospital.

"With the doctor's help, now he is out of danger."

Army field hospital

Health ministry official Ahsan insisted that medics could cope.

"The hospitals are not yet overburdened," he said.

But, just in case, the army has erected a 20-bed tent field hospital in the grounds of the government's Dhaka Medical College Hospital, ready for further cases.

"With the current measles outbreak, the health ministry told us to set up a field hospital," said the hospital director, Brigadier General Md Asaduzzaman.

But there are other challenges ahead.

Bangladesh has experienced heavy rainfall in the last few weeks -- bringing with it a rise in mosquitoes that carry the deadly dengue virus.

"We hope the measles infection rate will decrease soon," said Asaduzzaman.

"With the dengue season in mind, the field hospital is expected to be effective in that crisis too."