Sixth death in Argentina as cause of mystery pneumonia outbreak is identified

An 81-year-old man is the latest to die in an outbreak of pneumonia caused by legionella in northwest Argentina, authorities have confirmed.

The cluster of 11 cases at a health clinic in Tucumán raised concerns because early testing appeared to rule out most of the usual causes of pneumonia, including legionella. 

But on Saturday, authorities said that the bacteria – which causes Legionnaires’, a relatively rare lung disease commonly linked to contaminated water or unclean air-conditioning systems – was behind the outbreak, which has so far killed six people. 

“While we share the pain of those who faced this outbreak and wish a prompt recovery of those still affected, we have to say this is good news,” said Humberto Debat, a molecular virologist at the National Agricultural Technology Institute in Argentina. 

“We are not dealing with a new pathogen or a new disease. We know how to contain this outbreak, how to prevent and treat this disease. Of all the possible scenarios, I think this is the most favourable in sanitary terms,” he told the Telegraph

Legionnaires’ disease can be treated with antibiotics, though the death rate can be as high as 40 to 80 per cent if left untreated. Older people, smokers and those who are immunosuppressed or have respiratory conditions are most at risk. 

‘Moderate’ risk remains

In a situation report on Monday, the World Health Organization said that the cases all developed symptoms of pneumonia, fever, myalgia, shortness of breath and abdominal pain between August 18 and 25. 

They are all linked to a health facility in San Miguel de Tucumán, a city some 750 miles northwest of Buenos Aires, and eight of those affected were healthcare workers. The WHO said the risk of further cases at the same clinic is “currently moderate”. 

“Sporadic outbreaks of legionellosis pneumonia have been reported in Argentina before. There are robust surveillance activities being implemented in the affected health facility. 

“Nonetheless, in the absence of an identified source of Legionella bacteria, the risk of developing Legionellosis for people working or hospitalised at the same health facility is currently moderate,” the agency said. 

Legionnaires’ disease was discovered and named in 1976 after an outbreak at a Philadelphia convention of the American Legion of veterans, and has emerged sporadically in the decades since.

It can be difficult to diagnose – as testing relies on targeting specific antigens, uncommon strains can slip under the radar, as likely happened in Tucumán. 

That the cause of the cases has been identified, and is known, will be a relief for many. But it is not uncommon for outbreaks to burn out before the source is established. 

For instance, three people died and 127 fell ill with a hemorrhagic fever in South Sudan in 2020 – Ebola was discounted but the exact cause remains unknown – while 16 people in North Cameroon died from a mysterious disease in 2017. Diagnoses ranged from monkeypox to leishmaniasis, but the outbreak had subsided before the response team arrived. 

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