The World Health Organization is investigating an ongoing global threat caused due to toxic cough syrups, the global body told Reuters on Friday.

In January, the WHO had named nine countries where contaminated cough syrups were on sale after the death of more than 300 infants across three continents had been linked to the medicines. Now, the WHO has added six more countries to the list where toxic cough syrups are suspected to be on sale, Reuters reported.

However, Rutendo Kuwana, the WHO team lead for incidents with substandard and falsified medicines, refused to name the six new countries on the list.

Deaths due to toxic cough syrups made the headlines in October when the WHO issued a global alert for four such medicines manufactured by the Haryana-based Maiden Pharmaceuticals. This was after authorities in the West African country of The Gambia linked 66 deaths, most of them due to acute kidney failure, to the four medicines.

In December, the WHO recommended not using two cough syrups made by Indian pharmaceutical firm Marion Biotech after Uzbekistan’s health ministry said that 18 children died after consuming the Dok 1 Max syrup manufactured by the company. In April, another Indian drugmaker was also found by the World Health Organization to have exported contaminated cough syrup to the Marshall Islands and Micronesia.

Last month, India said it will allow the export of cough syrups only after samples are tested at specified government laboratories.

Also read: India’s cough syrup testing regime has a deadly blind spot

On Friday, WHO official Kuwana told Reuters that contaminated cough syrups could be found in the markets despite bans as adulterated barrels of propylene glycol, a key ingredient of such medicines, have a shelf life of two years.

Those involved in contamination of medicines, substitute propylene glycol with toxic alternatives like ethylene glycol and diethylene glycol because they are cheaper, experts told Reuters.

“WHO’s working theory is that in 2021, when prices of propylene glycol spiked, one or more suppliers mixed the cheaper toxic liquids with the legitimate chemical,” Kuwana told the news agency.

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