Very much in line with countries like the UK, flu is back in the headlines, with everyone being exhorted to behave themselves so as not to spread it – and those considered vulnerable encouraged to roll up their sleeves and receive vaccinations.
National health institute Dr Ricardo Jorge announced today that Portugal “has entered an epidemic phase of influenza with an increasing trend, registering a rise in confirmed cases, including hospitalisations in intensive care.
“Data relating to influenza activity in this 2025-26 season (…) showed that in week 48, which began on November 24, influenza activity is epidemic,” Raquel Guiomar, head of the National Reference Laboratory for Influenza and Other Respiratory Viruses at INSA, told Lusa.
In the last two to three weeks, there has been “an increase in the number of laboratory-confirmed cases of influenza virus infection” reported by the Sentinel Physicians Network.
The INSA Epidemiological Surveillance Bulletin for Influenza and other Respiratory Viruses shows that in the week of November 24-30, an increase in the incidence rate of severe acute respiratory infections was observed compared to previous weeks, reaching 10.5 cases per 100,000 inhabitants (in other words, a minuscule proportion of the population).
The age groups from zero to four years and 65 years upwards ‘showed the greatest increase’, with the elderly being most affected.
This week, 82 severe cases of acute respiratory infection were admitted to the Local Health Units (ULS) that reported data, with 10 admissions to intensive care units (ICU).
“All cases had underlying chronic disease and a recommendation for seasonal flu vaccination, three of whom were vaccinated. This week, the proportion of flu in ICUs was 6%, having increased compared to the previous week (1.6%),” states INSA’s bulletin.
Raquel Guiomar explained that, normally, the severity of the disease can be associated with the virus that is circulating, but often also with the individual conditions of each patient (and these invariably are elderly).
Regarding viruses that are circulating, the researcher stated that the viruses infecting the human population are of two types, A and B, and that at this time of year, influenza A viruses are primarily circulating.
“We have been detecting both subtypes of the influenza A virus, both the AH1N1 and the AH3N2 viruses,” with a slight predominance of AH1N1 at the moment.
However, she stressed that the co-circulation of the two subtypes of influenza A virus may change in the coming weeks.
Raquel Guiomar said that, in recent weeks, the AH3N2 subtype has received greater attention nationally and internationally, explaining that this virus, which circulated in the northern hemisphere last season and also in the southern hemisphere, has evolved and acquired mutations that may increase its transmission and infection capacity.
These mutations distinguish it from viruses of the previous era and from what is contemplated in the 2025-2026 vaccine.
According to the researcher, the new subgroup of viruses from the AH3N2 subtype, designated K, has already been detected in Portugal and represents about 45% of the AH3N2 viruses characterised so far.
Asked if it is likely to grow in the coming weeks, she stated that it is a possibility, given its characteristics, noting, citing European data, that in countries that had an earlier outbreak than Portugal, these were the viruses that experienced an increase in circulation as soon as the flu season began.
Raquel Guiomar also said that the epidemic arrived “three to four weeks earlier” than usual in Portugal, approaching the pattern observed in 2023-24.
“But we haven’t reached peak activity yet. Essentially, we are currently experiencing epidemic flu activity with an increasing trend,” she stressed.
Regarding other respiratory viruses, SARS-CoV-2 circulation is currently reduced, and respiratory syncytial virus (RSV) activity remains low, although it may increase in the coming weeks.
The ‘talking up’ of flu began last month when health minister Ana Paula Martins forecast a difficult winter. The reality is that winters in the SNS health service are always difficult because of underlying staffing/ management problems.. Flu just provides an inconvenient cherry on a very precarious cake – and this year (like with many others) the flu vaccine does not take into account ‘mutations’ in all the virus subtypes that are circulating.
Source: LUSA
