Economy 22 February 2024, 12:25pm

Epidemiological data hint at turnaround in flu season in Hungary

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More people with influenza and RSV infection were hospitalised in Hungary on the 7th week of 2024 than a year earlier, while there were fewer hospitalisations due to COVID-19. Almost 42% of those in hospital with severe acute respiratory infection (SARI) were children aged 2 and younger, and more than 83% of RSV patients belong to this age group. A bit less than half of those seeking medical help with acute respiratory infection (ARI) were aged 0-14 (over 142,000) and 40% of those showing flu-like symptoms were also in this age group. 70% of those in hospital with COVID-19 were aged 60 and older.

The flu season generally peaks between the 7th and 10th week of the year, but the highest figures can vary greatly from one year to another. The coronavirus pandemic, for instance, put a serious dent into the spread of the flu (see graph below).

The number of people seeking medical help with influenza-like symptoms per 100,000 population (620.2) was higher than currently two times in the past 12 cold seasons (in 2014/15, 2017/18).

For the 52nd week of 2023, the NNK published only a couple of figures, hence the gaps in the graphs. The timeline on the second graph goes up only to the 7th week for a closer look.

The epidemiological curve flattened slightly and this may well be the sign of a turnaround.

On the 7th week of 2024, a total of 289,100 people sought medical help with acute respiratory infection (ARI), of whom 60,100 (20.8%) had flu-like symptoms. The former figure marks a 1.4% drop and the latter a 1.5% rise over the 6th week.

We can also compare the ARI and flu numbers for 100,000 inhabitants. The epidemic has been more severe in 2023/24 than in 2022/23, apart from a few weeks.

We need to highlight that this year authorities perform more tests than a year ago, even though the number of samples tested remains extremely low (359 in total on a national level last week, down from 397 a week ago). The early zeal has abated by now, though. While initially six, eight, and even ten times more samples were tested, the multiplier is now just around two (in terms of the cumulated number of tests that is).

The COVID-19 positivity rate dropped further to 3.1%, while after a sharp rise on the 6th week the influenza positivity rate retreated to 36.5% from 42.6%. The positivity rate for the respiratory syncytial virus (RSV) rose further to 10% from 7.8% on the 6th and 6.0% on the 5th and 4th weeks.

If we take a look at the positivity rates on the individual weeks, we find that there was a turnaround on the 2nd week, with the influenza positivity rate (14.0%) higher than the Covid positivity rate (13.6%) for the first time in the current flu season. As noted above, the gap has widened considerably since then.

If you're wondering how the weekly positivity rates might turn out, here's how it went down last year, not that it is any guarantee that it will be repeated, but still it can serve as a kind of guidance.

As regards all samples tested up to the 7th week, the Covid positivity rate continues to stand out, but the flu positivity rate is coming up fast and will be higher in just a few weeks.

The share of coronavirus in all samples tested (orange lines) was a lot smaller a year ago (11.9%) than currently (21.8%), while the percentage of influenza in the samples (green lines) is about half now (14.1%) than on the seventh week of 2023 (31.8%).

As regards the prevalence of respiratory syncytial virus (RSV) in the samples (blue lines), the situation is much better in the current cold season than in 2022/23, with the share only at 3.1% on the 7th week this year versus 11.1% a year ago. Note that these are the percentages of the select pathogens found in all samples tested up to the 7th week.

People tested positive for influenza and RSV had to be hospitalised for the tenth consecutive week in this flu season. The 47th week was the first one when one of the samples showed influenza infection (up at 678 in total by the end of the 7th week). Other pathogens identified between the 40th and 7th week were SARS-CoV-2 (1,047), respiratory syncytial virus (RSV, 147), adenovirus (4), parainfluenza (6), human metapneumovirus (HMPV, 34, and rhinovirus (40).

THERE WERE 268 PEOPLE IN HOSPITAL WITH SARI ON THE 7TH WEEK, VERSUS 343 A WEEK AGO. 7.5% OF THEM WERE TREATED WITH COVID-19, DOWN a tad FROM 7.6% A WEEK EARLIER, WHILE ALMOST A quarter OF THEM (24.3%) WERE TREATED WITH INFLUENZA, down FROM 30.6% ON THE 6TH WEEK, while THE SHARE OF RSV PATIENTS rose further TO 22% from 18.1%.

The graphs below show a comparison with the previous 'flu season'. In 2022/23, there were no reports of people with Covid in hospitals, but that doesn't mean there weren't any (there were 100 on the first week of 2023, so it's a pretty safe bet that not all of them got to that stage overnight).

The second chart depicts the number and share of people infected by influenza virus who are currently in hospital. As you can see (orange columns, light blue curve), this 'flu season' is much worse in this respect than the previous one. The chart starts on the 49th week because that was the first week in this season when someone infected with influenza virus had to be hospitalised.

We have the same graph for respiratory syncytial virus (RSV), which shows that this infection was more severe in the previous 'flu season' up to the sixth week, but there was a turnaround on the 7th week. Although the number of people treated with RSV in hospitals declined, their share as a percentage of all people hospitalised with SARI picked up on the seventh week of 2024, while it had been already dropping from the 5th week in the previous flu season.

Another important indicator of the severity of an epidemic is how many of those hospitalised end up in the intensive care unit.

As mentioned above, there were 268 people with SARI in hospital on the week under review, down from 343 a week earlier. 28 of them were in the ICU, which corresponds to a 10.4% ratio, which figures compare with 43 and 12.5% a week earlier.

41.8% of those hospitalised with SARI were children aged 2 years or younger (up from 35.9% a week ago), while 26.9% of them were aged 60 and over (down from 33.5% on the 6th week). For the second time in this flu season, both the number and share of children aged 2 years or younger in hospital with SARI came in higher than the corresponding figures for those 60 and over.

The COVID-19 vaccination coverage of Hungarians aged 60 and older is dramatically low even by European standards, the latest update by the European Centre for Disease Prevention and Control (ECDC) shows.

We have no current data on the ongoing administration of flu shots, only figures for the past five flu seasons. These show that demand for vaccination surged during the coronavirus pandemic, and then petered out largely to previously observed levels. (Note that these figures show only the administration of free-of-charge 3FLUART influenza vaccine, i.e. they do not include shots GPs can prescribe at the request of their patients.)

We also know that merely 1.3% of the 3-18 age group got these free-of-charge flu shots in the 2022/23 flu season, following 1.7% in 2021/22, 3.9% in 2020/21, 1.4% in 2019/20, and 1.3% in 2018/19.

Half of those with ARI are children

Finally, we have an age breakdown both for ARI and flu patients. Children up to the age of 14 are on top of the ARI age rankings in terms of numbers, and for the fourth time this season they are also on top in the flu rankings, while the second hardest-hit cluster is the 15-34 age group. The right-hand charts show the share of people with aARI and flu-like symptoms by age group.

Looking back on the 2022/23 data we find that the 0-14 age group was the hardest hit throughout the flu season in terms of ARI, while in terms of flu-like symptoms they were the most affected age group between the 3rd and the 15th week of this year, i.e. from mid-January to mid-April.

On the 7th week this year, more than 142,500 children sought medical help with ARI, 49.3% of all people that turned to the doctor with some respiratory infection. They also stand out when it comes to flu-like symptoms (almost 41% of all), with their number up at nearly 24,500 from over 23,800 a week ago.