Influenza epidemic keeps tapering off in Hungary

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 (459.7) was higher than currently three times in the past 12 cold seasons (in 2014/15, 2017/18, and 2022/23).

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 9th week for a closer look.

THE EPIDEMIOLOGICAL CURVE FLATTENED FURTHER FOR THE third CONSECUTIVE WEEK, confirming A TURNAROUND.

On the 9th week of 2024, a total of 251,900 people sought medical help with acute respiratory infection (ARI), of whom 44,500 (17.7%) had flu-like symptoms. The former figure marks a 11.9% drop and the latter a 19.2% decline over the 8th 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 nine weeks, and the 9th is one of them.

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 (324 in total on a national level last week, down from 398 a week ago).

The COVID-19 positivity rate dropped further to 1.2%, and the influenza positivity rate fell sharply to 24.1% from 36.9%. The positivity rate for the respiratory syncytial virus (RSV) also decreased to 9.9% from 11.6%, which comes after three consecutive weeks of growth.

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. The gap has widened considerably, reaching 38.8% percentage points on the 6th week and has since then come down to 22.8%.

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 9th week, the Covid positivity rate continues to be the highest, but the flu positivity rate is coming up fast and could be higher shortly.

The share of coronavirus in all samples tested (orange lines) was a lot smaller a year ago (11.0%) than currently (19.2%), while the percentage of influenza in the samples (green lines) is less than half now (16.4%) than on the ninth week of 2023 (40.1%).

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 4.1% on the 9th week this year versus 11.2% a year ago. Note that these are the percentages of the select pathogens found in all samples tested up to the 9th week.

People tested positive for influenza and RSV had to be hospitalised for the 12th consecutive week in this flu season. The 47th week was the first one when one of the samples showed influenza infection (up at 903 in total by the end of the 9th week). Other pathogens identified between the 40th and 9th week were SARS-CoV-2 (1,060), respiratory syncytial virus (RSV, 225), adenovirus (6), parainfluenza (6), human metapneumovirus (HMPV, 60, and rhinovirus (45).

THERE WERE 284 PEOPLE IN HOSPITAL WITH SARI ON THE 9TH WEEK, VERSUS 357 A WEEK AGO, which was THE HIGHEST FIGURE IN THIS FLU SEASON. 3.5% OF THEM WERE TREATED WITH COVID-19, down FROM 7.6% A WEEK EARLIER, WHILE MORE THAN A FIFTH OF THEM (22.5%) WERE TREATED WITH INFLUENZA, DOWN FROM 23% ON THE 8TH WEEK, WHILE THE SHARE OF RSV PATIENTS remained fairly unchanged at 27.8% (vs. 28%).

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 following 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' was worse in this respect than the previous one up to the 8th week, but - at least in the number of influenza patients hospitalised - we see an improvement on the 9th week. The ratios are largely the same for both years. 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. Both the number of people treated with RSV in hospitals and their share as a percentage of all people hospitalised with SARI dropped some on the 9th week of 2024, but the RSV-related hospitalisation is now a lot worse than a year ago.

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 284 people with SARI in hospital on the week under review, down from 357 a week earlier. 31 of them were in the ICU, which corresponds to a 10.9% ratio, which figures compare with 42 and 11.8% a week earlier.

46.5% of those hospitalised with SARI were children aged 2 years or younger (up from 43.1% a week ago and the highest in this flu season yet), while 22.5% of them were aged 60 and over (down from 28.6% on the 8th week). For the fourth 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 sixth 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 ARI 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 9th week this year, more than 127,000 children sought medical help with ARI, 50.4% of all people that turned to the doctor with some respiratory infection. They also stand out when it comes to flu-like symptoms (more than 42% of all), with their number down at 18,800 from over 22,200 a week ago.

Cover photo: Getty Images