Three people have died this week in Argentina due to pneumonia of unknown origin, local health authorities said on Thursday.
Six others have been infected, experts say as they ruled out Covid, influenza, and Hantavirus as causative agents, according to local news reports.
At a press conference on Thursday, Luis Medina Ruiz, the minister of public health of the Tucumán province, reported the death of a 70-year-old patient and the identification of three employees of the medical facility with symptoms.
"What these patients have in common is the severe respiratory condition with bilateral pneumonia and compromise in images [x-ray] very similar to Covid, but that is ruled out," Dr Ruiz said on Wednesday.
Of the nine people found to be infected so far, eight were reportedly health workers, and one of them was an ICU patient treated at a private clinic in Tucumán.
"She was hospitalised and underwent surgery for a gallbladder problem. She was re-operated twice. From then on, an infectious pulmonary disease took place, the date of which coincides with the onset of symptoms in the other patients, around August 20," Dr Ruiz said of the patient.
"Although it is not yet clear which came first, at first she was considered patient zero, but she is under study based on the deepening of the analyses that are being carried out," he added.
Authorities say the symptoms of the mysterious illness were first reported between 18 and 22 August.
"It is very similar to Covid, hantavirus; it can be viruses or bacteria," director of epidemiology of the provincial health system, Dr Rogelio Calli, said at a press briefing on Tuesday.
SALUD PÚBLICA: El ministerio de Salud Pública informó sobre la situación sanitaria del brote de neumonía bilateral. Nota: https://t.co/GPqHj4FNtE pic.twitter.com/UWIg5lpSk3
So far, tests for Covid, hantavirus, and some strains of legionella have yielded negative results, the ministry said.
"We continue to carry out the research protocol for blood cultures, sputum cultures, urine cultures, and all the viruses and bacteria that we have available in the province," authorities said.
The medical facility has been placed under preventive isolation for seven days as authorities study the outbreak's origin.
"The most important thing is that if someone had a working relationship during those days with these patients and presents any symptoms, they present themselves at our on-call services and report it," they added.
"This situation is unpredictable, in principle, more than eleven days have passed, each patient has a different evolution, but you have to wait for evolution since it is a disease that there is still no knowledge of its origin, therefore, the evolution is also unpredictable," Dr Ruiz said.
The epidemic intelligence team of the European Centre for Disease Control is reportedly monitoring the situation in Argentina and scientists at the World Health Organisation are also tracking the situation.
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