Respiratory viruses have not responded to the usual patterns that they had followed for decades for three years. This winter the seasonality of the flu seemed to return, which had behaved abnormally since the outbreak of the covid (and the measures to stop it). But an unexpected second wave hits Spain at the gates of spring, at a time when infections were normally in free fall. These infections, however, do not seem especially serious.
According to the latest epidemiological report from the Carlos III Health Institute, “The rate of influenza in primary care describes a second seasonal wave of influenza associated with the circulation of influenza B viruses”. The highest incidences are being observed in children under 15 years of age, although all age groups are experiencing the upturn.
Amparo Larrauri, head of the Influenza and Other Respiratory Virus Surveillance Group at the National Epidemiology Center, explains to EL PAÍS that it is not uncommon for there to be second waves of influenza, but that it is rare for the two to be so far apart. The first, caused mainly by influenza A, reached its peak in mid-December, and the one that now affects Spain began to grow at the end of January.
“The flu has always been unpredictable, but it is true that we had many seasons in which all the seasonal waves reached their maximum between the end of December and the end of January, although there have been some exceptions of late flu that arrived in March,” he says. Larrauri. For the rest, in his opinion, more than the unusual of the dates, we are not facing anything “especially abnormal” in terms of its virulence: “There are no extraordinary hospitalization rates and the severity indicators are not alarming,” he justifies.
This seasonal behavior was completely altered with the covid pandemic. In the 2020-21 season, practically no respiratory pathogens other than coronavirus circulated. In 2021-22, a small flu epidemic wave was already observed at its usual time, before Christmas, but at that time the omicron variant arrived, displacing the other viruses. The flu subsided and only rebounded when the omicron began to subside. There was then a very late and long new wave, which lasted practically until the summer, something completely anomalous.
The rebound is collected by epidemiological bulletins, which take data from health centers, and is having an impact on the sale of anti-flu drugs, which have also experienced growth in recent weeks. According to data from the Health Market Research (HMR) consultancy, in the eighth week of the year, pharmacies invoiced 23 million euros in remedies that are used to alleviate viral symptoms, falling into the categories of anti-flu; analgesics and antipyretics; expectorants, cough and throat and nasal decongestion. It is practically double that on the same dates last year.
In the current season, the flu began to have an incidence in autumn, as is usual. Then it was the subvariants of the A that made their way. They are more volatile and mutate more than B, which worries specialists less about its potential to cause large (and serious) epidemics. Vicente Martín, from the Spanish Society of Primary Care Physicians, explains that having fewer variations often means more people are immune to this variety of the virus because they have defenses.
This may be one of the reasons why it is spreading, especially (although not only) in children under 15 years of age. Ana Fernández-Sesma, professor of microbiology at the Mount Sinai School of Medicine in New York, explains that many children who have not had contact with the virus until now are probably contracting the flu. “The restrictions of the pandemic, the use of masks and social distance have stopped the flu for the last few years. But we knew it was going to come back,” she says.
Fernández-Sesma attributes this wave to this probable drop in immunity, together with a general drop in temperatures and, “probably, the removal of the mask on public transport.” “It will not be more worrisome than other seasons, but you have to be aware, above all, of the vulnerable population, which perhaps has not been vaccinated as much as in other years,” he adds. The professor predicts that over time, probably next year, we will return to the usual seasonality, with some “strains more serious than others”, although this will also depend on how the covid behaves.
For the moment, the coronavirus has not yet rebounded significantly. Since the last wave, which peaked last summer, it has remained at low levels, with small rises and falls that have not hindered a steady drop in hospitalizations. According to the latest health datathere are 84 people with SARS-CoV-2 in intensive care throughout Spain, the minimum number since the pandemic began.
The biggest problem that this wave of flu is causing, as was the case with previous covid ones, is being experienced by primary care. Isabel Jimeno, from the Spanish Society of General and Family Physicians (SEMG), says that consultations are noticing these increases and asks for a tool that they do not have in health centers: the flu diagnostic tests that they do sell in pharmacy. “We do the covid test, which confirms or rules out this virus. But for the flu very often it is the patients who come in with their own diagnosis,” she points out.
The latest data from Carlos III already seemed to show the beginning of stabilization in this flu wave. Larrauri believes that it is possible that we will see it consolidate this week, which would mean that the peak is very close. “But since the flu is unpredictable, we can’t say for sure,” he clarifies.
