The death toll from measles in Bangladesh has topped 1,000 children since March, health officials said Wednesday, admitting that failures in a vaccination drive may have fuelled the outbreak.

The South Asian nation of 170 million has recorded 1,002 deaths and 187,484 infections among children, making this year’s outbreak the country’s deadliest in decades, according to the Directorate General of Health Services (DGHS).

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

Complications can include brain swelling and severe breathing problems. Although anyone can catch the disease, young children are particularly vulnerable.

The disease has kept spreading in Bangladesh even as health authorities rolled out a mass vaccination drive to combat the outbreak.

DGHS spokesman Zahid Raihan said more than 18 million children had been vaccinated so far, and teams were searching for those who had missed inoculations.

“We couldn’t achieve herd immunity,” Raihan told AFP.

Official figures show that around four million children were left out of the campaign, leaving pockets of vulnerability that experts say have fuelled the outbreak.