Catalonia has today made masks mandatory in health centers to reduce the impact of a flu epidemic that this Christmas has put a strain on emergency services in outpatient clinics and hospitals. The Ministry of Health has proposed, without success so far, that the measure be mandatory throughout Spain.
Different subtypes of influenza viruses circulate, as is usual in flu epidemics. No new mutations have been detected that increase the contagiousness or virulence of any of them.
This season the A(H1N1) subtype predominates, representing 70% of the cases analyzed, reports Antoni Trilla, epidemiologist at the Hospital Clínic of Barcelona. This is the virus that reemerged in the 2009 flu pandemic and has circulated since then without causing any major public health crisis.
Another 20% of cases are due to subtype A(H3N2), which has been circulating since 1968 and has a somewhat higher risk of causing serious complications in older people, reports Trilla.
Flu vaccines change each season to adapt to the strains of the virus that are most likely to circulate. They immunize against three (or four, depending on the vaccine) different varieties of the virus. They are made following the instructions of the World Health Organization (WHO), which says what the composition of the vaccines should be months in advance so that manufacturers have time to produce them. Therefore, some years the viruses that circulate do not match those expected and the effectiveness of the vaccines is reduced.
This season the vaccines match the specific strain of A(H1N1) that is circulating, reports the European Center for Disease Prevention and Control (ECDC) in its latest weekly report on communicable diseases. Therefore, it is expected that they offer good protection to reduce the risk of contagion and complications of the virus subtype that is more common this winter.
The vaccines also match the B virus, which circulates but is a minority.
On the contrary, the concordance with the A(H3N2) subtype is somewhat lower, reports the ECDC, so it is to be expected that the protection against this subtype will be lower.
It is a normal flu epidemic, comparable to those that were common in the years before the covid pandemic. There is no relevant difference compared to previous epidemics in terms of the contagiousness or virulence of the viruses that circulate. Nor is there an increase in mortality greater than that of a normal flu epidemic, according to the Mortality Monitoring (MoMo) data of the Carlos III Health Institute, which is updated daily.
In Spain, flu epidemics take on average about four and a half weeks to reach the peak of infections and another four and a half weeks to decrease again, according to a study by the Carlos III Health Institute published in Eurosurveillance that reviewed data from eighteen winters since 2001 to 2018.
The current epidemic took off shortly before Christmas so, if it conforms to the average, it will reach its peak in mid-January. In Catalonia, an analysis by the computational biology group Biocomsc, of the Universitat Politècnica (UPC), predicts the peak around January 11, with a margin of uncertainty of several days, reports researcher Clara Prats.
Afterwards, infections will reduce again and the epidemic should end in mid-to-late February.
In the last flu epidemic prior to the state of alarm of the pandemic, in which the A(H1N1) virus subtype predominated just like this year, 3,900 deaths occurred in Spain due to the flu, according to a study by the Health Institute. Charles III. On that occasion, 619,000 people with confirmed flu were hospitalized during the epidemic. Vaccination coverage in people over 65 years of age was 53.5%, a percentage similar to what is expected this season while waiting for definitive data to be available, so a similar mortality is foreseeable in the current epidemic.
Studies based on data from other years raise the number of deaths caused by flu epidemics in Spain to 6,000, reports Antoni Trilla.
“Vaccination is the best way to prevent influenza,” highlights the WHO. Other ways to avoid flu infections, according to the health organization, are: wash your hands regularly, since flu viruses are frequently transmitted by touching your mouth, nose or eyes with your hands; Cover your mouth and nose with a tissue or the inside of your elbow, but not your hand, when coughing or sneezing; dispose of tissues correctly; stay home if you feel unwell; and avoid contact with sick people if possible.
For its part, the ECDC recommends “wearing a mask in closed public spaces”, but warns that “the mask should be used correctly to obtain the desired effect” and that “it should be used together with other prevention measures such as avoiding close contact [with other people] and maintain good hand hygiene.”
The flu vaccine takes two weeks to induce effective protection, since the immune system needs these two weeks to produce specific antibodies that will protect against the flu virus. If a person is vaccinated this week, they will not be protected during the period in which the epidemic will reach its peak of infections and the risk of infection will be highest. Yes, it will be in the following weeks, when Spain will still be in an epidemic situation, although the infections will decrease.
An additional drawback to getting vaccinated now is that it may be difficult to get the vaccine at a time when primary care centers are strained by the influx of patients with respiratory infections.
