Influenza A viruses and the new Covid strain threaten Christmas: "There are more cases than are recorded"

Masks are back. In reality, they never completely left, they stayed in a drawer waiting for a new virus. If you look around you will find more than one face half covered. Has Covid returned? No, this time it is influenza A and some preventive behaviors against the coronavirus did catch on. “We are at the beginning of the epidemic. In two weeks there will be many more cases,” emphasizes Francisco Sanz Herrero, secretary of the Tuberculosis and Respiratory Infections Area of the Spanish Society of Pulmonology and Thoracic Surgery (Separ)..

With the data collected by the Acute Respiratory Infection Surveillance System (SiVIRA), which is carried out by the Carlos III Health Institute (ISCIII), an ascending curve is seen, a new wave of respiratory infections in which the A strain of the flu and Covid cases are the protagonists. “We still have time for people who can to request the vaccine [both flu and Covid] to protect themselves against a serious infection and its complications,” insists Sanz Herrero..

The latest weekly report from SiVIRA, which accumulates records until December 17, shows an increase in flu activity and RSV infection both in primary care and in hospitals. In the case of Covid-19, there is an uneven growth in cases in both scenarios. Cases of acute respiratory infections (ARIs) have risen 51% in the last week: the global rate rises from 523.4 to 793.9 cases per 100,000 inhabitants. By age group, the highest rates of ARIs are observed in children under 1 year of age and 1-4 years of age..

What is influenza A like this year?

The truth is that, as Sanz Herrero points out, “we have recovered the usual dynamics of the seasonal epidemic”. After several years with Covid as the protagonist, “we are seeing that first RSV (respiratory syncytial virus) infections arrive in children and weakened patients, then there is a growth in influenza A cases and finally, in a month, the “B”. And he does not hesitate to say that “currently there are more cases than are officially recorded”.

According to SiVIRA, 98.6% of the influenza viruses identified are type A (30.1% of AH3N2 and 69.9% of A(H1)pdm09 among the subtypes) with 31.1% of non-subtyped A viruses. “The strain with the greatest circulation is the one contained in the vaccine recommended for this year,” says Sanz Herrero..

The Separ spokesperson remembers what the infectious process is like. “It lasts five to seven days in which there is a feverish process and difficulty breathing and even mucus”. If these symptoms persist over time or worsen, “you should make an appointment with your doctor to avoid complications.”. He also points out that “antibiotics should not be used if we are dealing with a virus.”. “The only thing it does is increase the number of bacterial resistance.”.

SiVIRA points to a very high growth in the rate of flu cases detected in primary care, which reaches 159.2 per 100,000 inhabitants, when in the previous week it remained at 68.2 infections.. In terms of income, the same thing also happens: it goes from 1.6 people to 2.9 per 100,000.

Severe forms may require hospitalization due to the onset of bronchitis. “You have to prevent the cough from getting worse and the mucus from changing color. If so, you should also consult,” repeats Sanz Herrero.. For this reason, the pulmonologist remembers that Covid preventive measures are “those that must be taken into account: return to tests, masks and maintaining preventive attitudes with people at risk.”.

What is the impact of the new Covid strain?

This week the WHO warned of surveillance of a new strain of coronavirus. The first thing to rule out is Covid-23, as was already rumored on social networks. From the CSIC Global Health Platform, Fernando González Candelas, states that “this variant cannot at all be considered a new virus.”. In fact, it only differs from its parental lineage BA.2.86 in one relevant mutation, in the Spike: L455S. However, it has a much higher growth capacity than BA.2.86 and in some countries, including Spain, its frequency is rapidly increasing.. This is what has led the WHO to put it on the list of variants of interest.”.

The virological reasons for this alarm are due to the fact that “what has been seen is that JN.1 follows the trend of other omicrons, in which over time they have changed their way of entering the cells, different from those they used the pre-micron variants, and the jump in JN.1 in terms of this characteristic (measured in the laboratory) is quite pronounced,” says another of the CSIC platform researchers, Mireia Coscollá Devís, director of PathoGenOmics at I2SysBio.

The data on the strains registered in SiVIRA point to a predominance in primary care of the XBB.1.5-like + F456L variant (53.50%), followed by XBB.1.5-like (16.87%) and BA.2.86 ( 14.81%). The predominant ones in recent weeks have been XBB.1.5-like + F456L (41.79%) and BA.2.86 (41.79%). Regarding JN.1, the latest report does not mention.

González Candelas, professor of genetics at the University of Valencia and Fisabio, details that “seasonal growth has been associated with one variant or another in recent years, but both the characteristics of the virus (and those specific lineages) and to the epidemiological conditions, which facilitate the increase in cases at certain times, such as the beginning of winter”.

And what does this translate into at a clinical level?. That is, what symptoms does it produce? As Coscollá Devís explains, “this change means that pre-micron variants would enter respiratory tract cells well (with certain mechanisms), but post-micron variants (and JN.1 in extreme form) would not enter these cells as well, but would do so in cells like those in the digestive tract that have slightly different input receptors.”.

Regarding the evolution over time, Coscollá Devís clarifies that “these findings are recent and must be confirmed, but these are the most relevant changes for the clinic that I have seen published recently.”. There is some data from antibody neutralization experiments, and some studies suggest that they would be less susceptible to the defenses generated by the recombinant variants.. “These are in vitro data, referring to very specific aspects of immunity, so they are not enough to fear that vaccines or previous infections do not protect.”.

What is the epidemic of respiratory syncytial virus in children like?

Pediatricians are optimistic because there are not as many cases as in previous seasons.

The ISCIII report records that the rate of RSV infection stands at 120.9 cases per 100,000 inhabitants, compared to 83.4 the previous week. By age groups, the highest rates of primary care are observed in the group of children under 1 year of age (1,565.7 cases per 100,000).

After the implementation of the immunization of children under six months of age against the virus responsible for their admission to the ICU, it is worth noting that in the same week last year this figure was higher. This year's hospitalization rate stands at 4 cases per 100,000 inhabitants, compared to 5.5 in the past, which reached 9 in previous weeks.. It should be noted that, at the same time, in 2022, the RSV peak had already been reached.