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Respiratory infections have now officially crossed the epidemic threshold across Spain, according to the latest weekly report from the Carlos III Health Institute, published this Thursday with figures covering 21 to 27 September. The national incidence rate climbed from 373 to 478.2 cases per 100,000 inhabitants, the first time this autumn that threshold has been passed.

 

A similar pattern had already emerged in the Region of Murcia days earlier, where respiratory infections rose 33% in a single week in late September, with Covid cases up 80% and flu up 65.6%.

 

The youngest children remain the most affected group in primary care. Infants up to one year old saw their infection rate jump from 2,802.3 to 4,013.8 cases per 100,000, while those aged one to four climbed from 1,554.9 to 2,161.5. In hospitals, the picture looks a little different, with those over 80 experiencing the highest rates, rising from 55.1 to 60.5, followed closely by infants under 12 months, whose rate climbed from 36.2 to 57.7.

 

Over in the Valencian Community, Covid incidence told a similarly sharp story, more than doubling from 52 to 117.2 cases per 100,000 over the same period, roughly twice the national rate at the time.

 

Despite the alarming headline figures, the Spanish Society of Epidemiology told 20minutos that crossing the threshold at this point in the year "is within the normal range" and "is not an anomalous development". As the society explained, "in previous seasons, the baseline threshold for the overall ARI rate is reached between weeks 38 and 39. We are currently in week 39." Experts point to the usual autumn mix of factors, the return to school, people back at work, and more time spent indoors, rather than any single virus driving the rise.

 

This builds on an increase already flagged nationally a few days earlier, when the flu positivity rate had doubled year on year to 8.2% and Covid positivity reached 16.7%, with infant infection rates more than doubling within a fortnight.

 

Covid itself showed a slight dip in the very latest week, falling from 232.1 to 223 cases per 100,000, though the overall rate across all ages still sits well above the equivalent period in the previous two seasons. The most striking figure in the latest report concerns hospital admissions. COVID-19 admissions among those aged 80 and over rose 83% in a week, from 9.1 to 16.7 cases per 100,000, making this group by far the most affected. Infants under one saw the second largest rise, from 1.9 to 6.2.

 

Experts explain the pattern among babies as a "classic" one, since newborns have no prior immunity to the virus, unlike older children and adults who carry some protection from vaccination or previous infection. Prevention efforts, epidemiologists say, should focus squarely on the very young, the very old, and those with chronic illness or weakened immunity, with vaccination remaining the key tool for these groups.

 

Vaccination campaigns are already well underway in several regions. Andalucía's flu and Covid programme began on 1 October with over €20 million invested in nearly two million doses, offering the high dose vaccine from age 75 for the first time this year.

 

On the question of whether vaccination should simply move earlier given Covid's tendency to surge in warmer months too, experts remain unconvinced. "It is technically impossible to predict months in advance the exact moment when a new summer or spring wave will emerge," the Spanish Society of Epidemiology noted, adding that fully vaccinating in early autumn still gives vulnerable groups the strongest protection heading into the months when flu, Covid and RSV typically circulate together.

 

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