October 18. 2021. 5:45

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Raised SARS-CoV-2 co-infection risk suggests other pathogens should not be overlooked


The increasing number of immunocompromised people exposed to COVID combined with the raised risk of co-infections of the SARS-CoV-2 virus and respiratory pathogens creates a double whammy that cannot be overlooked.

High hospitalisation rates of coronavirus infections among immunocompromised people still constitute a concern for public health even after the rollout of the COVID-vaccine campaign.

Immunocompromised people have weakened immune systems which affect the ability to fight infections and, in certain cases, even hamper the response to vaccines.

This condition exposes sufferers not only to COVID but to other pathogens as well.

“For instance, there is an increased risk of Legionnaire’s disease in those patients and I think there will be a lot more publications in the future that confirm that,” said Susanne Lee, a microbiologist with many years of experience in British public health agencies.

Legionnaires’ disease occurs by inhaling aerosols carrying the Legionella bacteria – which develop primarily in warm, stagnant water – with infection leading to a deadly form of pneumonia.

To make things worse, groups at risk from COVID-19 and Legionnaires’ disease are largely the same.

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Co-infection risk

Another worrying aspect is co-infection risk and secondary infections of coronavirus and other pathogens, already observed during the 2009 influenza A (H1N1) epidemic.

At that time, the main concern was misdiagnosis due to availability bias, as treatable bacterial or parasitic infections were mistakenly labelled as influenza, research showed.

A case of co-infection of COVID-19 and legionellosis was first reported in Japan’s Asahi general hospital, where an 80-year-old Japanese national was hospitalised upon his return from a Nile cruise.

As symptoms of malaise, diarrhoea and cough had worsened after a week, the man was tested both for Legionella bacteria and for SARS-CoV-2 virus, resulting positive for both infections.

The Japanese man was in a risk group category as he had diabetes mellitus and died several weeks later, though the doctors who examined him, believed that the Legionella treatment was probably successful and that COVID-19 was the likely cause of death.

In a paper, the doctors who treated him highlighted the importance of differential diagnosis during the current COVID-19 pandemic, “so we do not miss the opportunity to diagnose other treatable causes of disease with similar symptoms.”

‘Precautions are needed’

A study conducted in China’s Qingdao city on 68 patients with severe acute respiratory coronavirus confirmed the presence of other common respiratory pathogens.

The research concluded that precautions are needed when dealing with COVID-19 patients who have coinfection with other respiratory pathogens.

“Detection of only L. pneumophila serogroup 1 antigen in urine is a suitable diagnostic approach for outpatient-acquired and travel-associated pneumonia, with varying sensitivity and specificity,” the author of the German study wrote.

A similar approach is suggested by health experts to check the presence of Legionella in the water system of public buildings.

“Clinicians treating patients positive for SARS-CoV-2 should be aware of possible co-infections with L. pneumophila and should use appropriate diagnostic approaches,” the author of the German study pointed out.