Daijiworld Media Network - Madrid

Madrid, Apr 19: A new population-based study presented at ESCMID Global 2026 has revealed that influenza infections were missed in a significant number of winter deaths in Spain, raising concerns over gaps in disease detection and mortality reporting.

According to the findings, influenza was detected in 11 per cent of winter deaths through postmortem testing, yet only 1.4 per cent were officially recorded as flu-related on death certificates. The study indicates that nearly 83 per cent of such cases went unrecognised during life or unreported after death.

Researchers analysed 857 deaths recorded during winter periods when overall mortality was about 12 per cent higher than expected, a trend often linked to seasonal respiratory infections. Postmortem swabs were collected within 24 hours of death and tested using PCR for a broad range of respiratory viruses.

Out of 94 individuals who tested positive for influenza, only 41.5 per cent had been hospitalised, and just 17 per cent had received a diagnosis within 30 days prior to death, highlighting the extent of underdiagnosis.

Lead author Lucía Argente-Colás from the University Hospital of Navarre said the findings were striking and pointed to a substantial gap in identifying infections before death. She noted that many individuals die at home where testing is less likely, while in some cases the illness may progress rapidly before medical attention is sought.

The study also found that in older adults and those with pre-existing conditions, symptoms of influenza may be mild or masked, leading to missed diagnoses. In such cases, death certificates often attribute mortality to chronic illnesses, even when a viral infection may have contributed.

Researchers emphasised that while detecting influenza postmortem does not confirm it as the direct cause of death, respiratory infections are known to accelerate deterioration in vulnerable populations.

The findings suggest that influenza may play a far greater role in winter mortality than currently reflected in official data. Experts have called for improved surveillance systems and broader testing strategies, particularly for high-risk groups and deaths occurring outside healthcare settings.