Economy 25 January 2024, 12:41pm

Flu season is more like Covid season in Hungary, epidemiological situation worsens

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While the public tends to call the winter months the 'influenza season', the period between the 40th week of 2023 and the 20th week of 2024 has been anything but so far. Coronavirus remains the key pathogen among respiratory infections even on the third week of this year, with half of hospitalised patients tested positive for SARS-CoV-2 and more than three quarters of them aged 60 and over. Almost half of those seeking medical help with severe acute respiratory infections were in the 0-14 year age group, which translates into nearly 91,000 children.

A word about the gap in the charts

The National Public Health Centre (NNK) first skipped the report for the 51st week of 2023 between Christmas and New Year. Then it published data only for the 51st week, but nothing for the 52nd week. Last week, it published its epidemiological report not only for the 52nd week of 2023 but also for the 1st week of 2024.

However, the report for the 52nd week was extremely concise, missing a host of key figures, including on the actual number of Hungarians turning to the doctor with severe acute respiratory infection, including flu-like symptoms, an age breakdown of those seeking medical help, incidence per 100,000 population, and hospital data altogether. This has caused unwanted breaks in our time series and graphs. We have asked the NNK if we could have more than just two paragraphs for the 52nd week but its press department did not dignify us with an answer. Hence the gaps remain.

Data worsen further

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).

A dip for the holiday season was anticipated, and - as discussed above - further moderation on the first week was not a shocker, either. Employees generally take their leave at the end of the year, there's the winter break in schools, and a heightened reluctance to go to the doctor "with a simple cold".

The number of people seeking medical help with influenza-like symptoms per 100,000 population was higher than currently only twice in the past 12 cold seasons (in 2016/17 and in 2018/19).

Here's a blow-up of the period in question:

On the 3rd week of 2024, a total of 197,200 people sought medical help with severe acute respiratory infection (SARI), of whom 28,600 (14.5%) had flu-like symptoms. The former figure marks a 11.8% increase and the latter a 15.3% growth over the 2nd week. Columns are missing for the NNK did not publish these figures for the 52nd week.

The graph below allows a comparison with weeks 40 to 3 of 2022/23, showing higher figures for this cold season both for the number of people that visited GPs with flu-like symptoms and of SARI "patients".

We can also compare the SARI and flu numbers for 100,000 inhabitants. Despite the relief observed between the 51st week of 2023 and the 1st week of 2024, chances are that the epidemic will be more severe in 2023/24 than in 2022/23.

We need to highlight that this year authorities perform way more tests than a year ago, even though the number of samples tested remains extremely low (309 in total on a national level last week, up from 221 a week ago but down from this season's high of 327 on the 50th week).

The number of samples tested on the 3rd week was higher than on the 2nd week, with the COVID-19 positivity rate all over the place - it is currently up at 16.8%, after hitting its lowest in this season on the 2nd week. Testing is almost non-existent and we may draw only extremely cautious conclusions from these findings as regards the bigger picture on the current epidemiological situation. This is basically the only set of Covid data authorities provide besides weekly wastewater sampling results. Looking at the numbers, however, it's a pretty safe bet that SARS-CoV-2 remains the key pathogen for the time being.

As regards all samples tested up to the 3rd week, the Covid positivity rate continues to stand out.

Covid infections trump flu infections

SARS-CoV-2 was the main pathogen found in samples early in the flu season last year too. Actually, the first time the share of flu viruses in samples was higher than the share of coronavirus occurred only at the start of this year in the 2022/23 flu season (after the green and orange lines crossed, see graph).

At the same time, we cannot even estimate when this turnaround will take place this year. In fact, it would be a surprise it if occurred at all. Why? Well, take a look at the two graph below! The share of coronavirus in all samples tested (orange lines) was about half than currently a year ago (14.3% vs. 29.2% currently), while the percentage of influenza in the samples (green lines) is way lower now than in the third week of 2023 (4.9% vs. 17.1%).

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 1.1% on the third week this year versus 8.0% a year ago.

For the seventh consecutive week in this flu season (or should we say Covid season?), however, people who tested positive for influenza virus and RSV also had to be hospitalised. The 47th week was the first one in this cold season when one of the samples showed influenza infection (up at 163 in total by the end of the 3rd week). Other pathogens identified between the 40th and 2nd week were SARS-CoV-2 (976), respiratory syncytial virus (RSV, 38), adenovirus (2), parainfluenza (4), human metapneumovirus (HMPV, 15, and rhinovirus (35).

There were 201 people in hospital with SARI on the 3rd week, versus 166 a week ago. 50% of them were treated with COVID-19, up from 47% a week earlier.

78 (77.2%) of the 101 COVID-19 patients were aged 60 and over, which compares with 62 (79.5%) a week earlier. The number of people in hospital with coronavirus infection jumped 30% from 78 a week ago.

14.4% of those hospitalised with SARI were children aged 2 years or younger (down from 24.1% a week ago), while nearly 63% of them were aged 60 and over (up from 55% on the 2nd week).

Another important indicator of the severity of an epidemic is how many of those hospitalised end up in the intensive care unit (or in the morgue for that matter). The NNK does not reveal mortality stats, though.

As mentioned above, there were 201 people with SARI in hospital on the week under review, up own from 166 a week earlier. 25 of them were in the ICU, which corresponds to a 12.4% ratio, which compare with 19 (11.4%) a week earlier.

Finally, we have an age breakdown both for SARI and flu patients. Children up to the age of 14 are on top of the SARI age rankings in terms of numbers, and for the first 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 SARI 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 SARI, 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.