Mystery cluster of pneumonia cases in Argentina being monitored by World Health Organisation

The World Health Organisation is monitoring a cluster of pneumonia cases from an unknown cause in Argentina, in an outbreak that so far has included three deaths.

The 10 cases are linked to a single private clinic in the city of San Miguel de Tucuman in the country's northwest, according to the Pan American Health Organisation (PAHO), the regional office of the WHO.

Tests for known respiratory viruses and other viral, bacterial and fungal agents were all negative, the PAHO said.

Authorities also say they have ruled out COVID.

Biological samples have been sent to Argentina's National Administration of Laboratories and Health Institutes for additional testing, which will include an analysis for the presence of toxins.

Dr Michael Osterholm, an infectious disease expert at the University of Minnesota, said given that the lungs are heavily involved, the cause is likely something the patients inhaled.

He first suspected Legionnaires' disease, which is caused by inhaling droplets of water containing Legionella bacteria, but tests have ruled that out.

Dr Osterholm said "mystery illnesses" do sometimes happen, and most often they can be explained by some local outbreak that does not have pandemic implications.

He said he expects more definitive information from Argentine health officials in the next five to seven days.