The head of the World Health Organization on Thursday called for increased production of cholera vaccines, highlighting what he called a "critical shortage" around the globe.

The UN health agency said 307,433 cases of cholera and 2,326 deaths have been reported in 26 countries up to July 28.

"The response continues to be affected by a critical shortage of the vaccine, as demand continues to outpace supply," WHO chief Tedros Adhanom Ghebreyesus said on X, formerly Twitter.

Some 105 million doses have been requested by 18 countries since January 2023 -- but only 55 million doses have been produced in the same period, Tedros added.

In a fresh situation update, the WHO said that between January and May 2024, the oral cholera vaccine stockpile "was entirely depleted".

Tedros urged "further investment in scaling up vaccine production", and called on all countries to spend more on "water and sanitation, and emergency preparedness to prevent further outbreaks".

The eastern Mediterranean region, Africa and southeast Asia have recorded the highest numbers of cases, said the WHO, which considers the global risk from cholera to be "very high" due to the growing number of cases and the shortage of vaccines.

The WHO says that after decades of progress against cholera, cases have been on the rise again since 2021, including in countries that had not seen the disease in years.

The cases registered so far should be interpreted cautiously due to potential reporting delays, the WHO said.

The disease, which causes severe diarrhoea, vomiting and muscle cramps, generally arises from eating or drinking food or water that is contaminated with the bacterium, according to the WHO.