MADRID – The coronavirus has wiped out other respiratory infections this winter, especially the flu. Keeping a distance, mouth guards and other corona measures have all but wiped out less-communicable viruses. That seems like good news.
Effects of temporary disappearance of flu not only positive
This season, only seven cases of flu have been detected in Spain. At this time last year, there were almost 7,000. Although figures vary slightly from country to country, data from the European Centre for Disease Prevention and Control (ECDC) show the same pattern. For instance, the number of infections during winter matches those during summer, meaning that there were almost no infections.
The influenza viruses have not been eradicated. They continue to circulate and it is unknown in what form they will return, once they are free again. Virologists and epidemiologists are worried because influenza mutates so quickly and they cannot see it now.
Since the beginning of the season, more than 315,000 tests have been carried out in Europe. But only 605 cases of influenza have been identified: 302 (49.9%) of type A and 303 (50.1%) of type B. In the US, the number of samples tested this year has reached 800,000. Likewise, 100 times fewer cases have been identified than in the previous season.
‘It is very surprising what is happening this year with viruses in the respiratory tract and even bacteria transmitted through the respiratory tract, such as meningococcal disease in children, which have not disappeared but have been drastically reduced,’ said Angel Hernandez Merino, expert of the vaccine advisory committee of the Spanish Society of Paediatrics. In general, from what we can tell, the number of respiratory infections has decreased. There is no specific data on colds and chills, but according to health workers working in the front line, there has also been a decrease there.
Pandemic is interfering
In recent months, patients and medical specialists have complained that the health situation caused by corona has impeded the correct diagnosis of many diseases, including cancer.
The World Health Organisation (WHO) warned that in some countries this could also happen with the flu. This does not seem to be the case in Spain or in Europe, because it is strictly controlled. For example, in the Madrid sub-region alone, 300 doctors take weekly samples between October and April. But the tests have always proved negative. In the case of other diseases, such as measles, there may well be less attention paid to detecting the disease.
Corona measures more effective against flu than corona
For epidemiologists, it is clear that the strategy against Covid-19 was more effective in drastically reducing the number of flu infections than the number of corona infections. This led to an extraordinary situation, which already arose last year in some countries that had taken initial measures against the coronavirus. South Korea and Singapore saw a big drop in the number of flu infections, says Jaime Jesus Perez Martin, specialist in preventive medicine and member of the Spanish Association of Vaccinology (AEV).
It is important to note that SARS-CoV-2 spreads ‘two to three times more easily’ than the flu virus. This is most likely by transmission through aerosols – small droplets suspended in the air indoors. However, experts believe that the flu vaccination, which has reached record numbers this year, may also have had an impact.
Manufacturers have to start producing the vaccines for the autumn. But due to the lack of infections, hardly any information is known about the flu viruses. Every year around this time, in late February, the WHO determines the composition of the vaccines for the next season. As a result, the manufacturers can then work to have them ready for September or October. However, now that is difficult because the virus is constantly changing. And as such, experts from the UN agency should give their opinion on the matter now.
In the absence of data, ‘a very worrying scenario emerges’, said Hernandez Merino. Because for the experts, ‘these doubts and uncertainties are terrible. Especially as there is no certainty about the type of virus against which the vaccines should be made’.
Two years ago, as an exception, the recommendations were made at the end of March. “At the last moment it turned out that a new virus variant had emerged” he explains. “And then we waited to see how likely it was this variant would circulate the following year.” Something similar could happen this year, taking into account the production time needed by pharmaceutical companies.
Lack of knowledge
For the southern hemisphere, WHO recommendations are usually made in August. But in 2020 they were published on September 25. This made it possible to take into account the viral infections that circulate in the northern hemisphere in winter. However, for the coming period, the experts are faced with an unprecedented situation.
Specialists now have to rely on the low circulation of the virus,’ says Perez Martin. ‘It is difficult to make recommendations precisely because of the lack of data. And the data from the southern hemisphere does not help much. Because countries such as Australia, South Africa and Argentina were the first to observe a dramatic decrease in the number of flu patients in the pandemic. Another possibility in this scenario is vaccination based on the previous year’s variants. But then one has to be pretty sure that no significant changes have occurred.’
Flu vaccination pays off
In any case, specialists believe that even if the vaccine is not as good or as specific as other years, it is always better to get vaccinated than not to. No matter how small the efficacy of the available vaccine, it is always better than nothing,’ says Hernandez Merino. It is estimated that vaccination in the 2019-2020 flu season prevented 26% of hospital admissions, 40% of ICU admissions and 37% of deaths.
However, less vaccination, combined with more harmful flu strains, could lead to a dangerous one next winter. Especially if measures against corona are relaxed or lifted or if the pandemic subsides. Furthermore, it is almost impossible to make predictions; ‘the flu is absolutely unpredictable’, says the AEV expert. However, ‘it is certain that the viruses are there, even in summer, they only need the right opportunities to go around again’. If we go back to ‘normal’ next year, there will be many viruses. This will include the flu virus, which will not go away and will circulate again. Protection will be even more important then.’
According to Florian Krammer, virologist and flu expert at the Icahn School of Medicine in Mount Sinai, the virus will not disappear, but some variants might. That would be a positive effect of Covid-19. Virologists and vaccinologists are also hopeful about the possible application of the RNA technology used in Pfizer’s and Moderna’s vaccines. And also about obtaining flu vaccines that are easier and quicker to modify,
On the other hand, experts are concerned about another aspect of the temporary disappearance of the flu. Hundreds of thousands of people normally get the flu every year. However, it is to be expected that they will have some immunity, at least for a while. If that has not been the case this winter, the next outbreak could make some of the population more susceptible. It is a possibility, but I think one year is too short a period to conclude that there is a reduction in general immunity in the population. If this phenomenon persists, it could happen, but this does not seem to matter now, concludes Pérez Martín.