Influenza A/H3N2 on the rise: imminent peak and alarm over pressure on UK hospitals

The influenza curve is still rising and the peak of cases is approaching, which could already arrive at the end of the month: last week, according to the Istituto Superiore di Sanità's RespiVirNet surveillance system, 695,000 Italians were put to bed with acute respiratory infections, about 100,000 more than the previous week and with a total since the start of surveillance of about 4 million cases, which suggests a record-breaking season that could exceed 16 million cases overall. Increasingly, influenza viruses are causing the contagions, especially A/H3N2, a type already known but which has circulated little in recent years and which this year also presented itself with a new strain that is said to have caused the lengthening of the flu season in the southern hemisphere, where contagions have remained high for at least a month longer than usual. Meanwhile, the 'super flu' epidemic is affecting several countries, with particular alarm in the UK where, according to the UK Health Secretary, it represents 'a challenge never seen since the Covid pandemic' for public health service hospitals.

"This week there is a sustained increase in the number of cases of acute respiratory infections recorded by RespiVirNet surveillance," stressed the director of the Iss's Department of Infectious Diseases, Anna Teresa Palamara, who points out, however, that the increase is "in line with the expected trend for this time of year". As for the peak, 'it is not possible to predict exactly when it will be reached': 'it is usually recorded between the end of December and the end of January, but in the coming weeks it is likely that the incidence of infections will remain high'. According to the weekly bulletin, in the week between 1 and 7 December, 12.4 out of every 1,000 Italians were affected by respiratory infections. Once again, the age group most affected was children under the age of 4, with an incidence three times higher (38 per 1,000) than the general population. Lombardy, Piedmont, Emilia Romagna and Sardinia are the regions with the most infections. As for circulating viruses, the quota of infections attributable to influenza viruses, which are responsible for about a quarter of cases of illness, is increasing. Among the influenza viruses, then, the H3N2 type is currently dominant. The other infections are mainly due to Rhinovirus, Adenovirus and Parainfluenza viruses. 'Let's remember the main prevention measures,' adds Palamara. "Vaccination, for which there is still time since the virus will still circulate for several weeks, strict hand hygiene, respecting the so-called respiratory etiquette, e.g. coughing into a handkerchief or into the crook of the arm, avoiding closed and crowded places in the presence of symptoms," he concludes.

The outbreak of 'super flu' reported this season in various countries, and with particular alarm in the United Kingdom, represents 'a challenge never seen since the Covid pandemic' for public health service (NHS) hospitals. This is the worrying message from the British Health Minister, Wes Streeting, echoing the concerns that have mounted in recent days on the island over a number of infections reported to be above average for this time of year, especially among children and young people, and a total number of admissions that has risen to over 2,600 patients per day. Streeting therefore took the opportunity to revive the controversy against the wage dispute of the resident doctors - newly specialised doctors who until recently were called junior doctors and traditionally underpaid within the NHS - who have gone back on strike despite the agreements of the past months on the increases granted in general to various categories of public services and healthcare by the current Labour government. Their new round of protests - the 14th in three years - has been proclaimed just before Christmas, with another five days of abstention from work starting on 17 December: and according to the minister it is likely to be 'the final straw' of a 'precarious situation' in hospitals. Chris Streather, Medical Director of Nhs in London and leading medical authority in the British capital, has however downplayed the extent of the sos related to flu cases. Assuring that the wave of infections remains for now 'well within the limits' of hospitals' response capacity and that the system is now 'better prepared' after the pandemic experience.

In the Southern Hemisphere, the flu season this year lasted at least a month longer than usual. The cause is most likely a new strain of influenza virus A/H3N2 (known as K) that has emerged in recent months. This is the finding of an analysis published in Eurosurveillance, a journal of the European Centre for Disease Prevention and Control. "Flu seasons vary somewhat each year in their onset, intensity, severity and duration," reads the study coordinated by researchers at the Doherty Institute, Melbourne. "Many factors contribute to this variability: temperature, rainfall, humidity, circulating virus subtypes, population immunity, even domestic and international travel." This year, the new element was the emergence during the season of a new strain of A/H3N2 virus. This is nothing new: something similar happened in 2019, for example, when a new version of the H3N2 virus forced a delay in the choice of the strain to be included in the flu vaccine, the researchers recall. The appearance of the new virus, this time, led to an increase in cases and the lengthening by at least a month of the season, which lasted until late November and whose after-effects are still being recorded. The profile of the sick also changed, with the average age dropping by about five years. On the other hand, no changes in the severity of the infection or a decline in the effectiveness of antiviral drugs were detected. Instead, a slight reduction in the protection conferred by the vaccine is likely, the researchers explain. 'Given the speed and size of K virus outbreaks in Australia and New Zealand and the rapid global spread, it is likely that they will expand further during the winter season in the northern hemisphere,' concludes the team, which urges countries to 'be prepared for the possible increased pressure on their health systems'.