Yesterday, Catalonia reinstated the mandatory use of masks in health centers to reduce the impact of the flu epidemic.
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As is common in influenza epidemics, several subtypes of influenza viruses circulate. No new mutations have been detected that increase the infectivity or virulence of any of these subtypes. This season, subtype A(H1N1) predominates, representing 70% of the cases analyzed, reports Antoni Trilla, epidemiologist at the Clínic hospital. This is a virus that has been circulating since 2009. Another 20% of cases are caused by subtype A(H3N2), which has been circulating since 1968 and has a slightly higher risk of causing serious complications in older people, reports thresh
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Flu vaccines change each season to adapt to the strains of the virus that are most likely to circulate. They immunize against several varieties of the virus. This season the vaccines match the specific strain of A(H1N1) that is circulating, the European Center for Disease Prevention and Control (ECDC) has reported. That is why they are expected to offer good protection against the subtype of the virus that is currently circulating the most. Vaccines also match the B virus, which is now in the minority. The concordance with subtype A(H3N2) is somewhat lower, so protection against this subtype should be expected to be lower.
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It is a normal flu epidemic, comparable to those in the years before the pandemic. There are no relevant differences compared to previous epidemics in terms of the contagiousness or virulence of the viruses circulating. Nor is there an increase in mortality higher than that of a normal flu epidemic, according to data from the Mortality Monitoring (MoMo) of the Carlos III Health Institute (ISCIII).
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In Spain, flu epidemics take an average of four and a half weeks to reach the peak of infections, and another four and a half weeks to decline again, according to a study by the ISCIII that reviewed data from 2001 to 2018. The ‘current epidemic started shortly before Christmas so that, if adjusted to the average, it will reach the peak in mid-January. In Catalonia, an analysis by the computational biology group Biocomsc, of the UPC, predicts the peak for January 11, with a margin of uncertainty of several days, reports researcher Clara Prats. Then the infections will drop again and the epidemic should end in the middle or end of February.
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During the 2019-2020 epidemic, in which the A(H1N1) virus subtype predominated, just like this year, there were 3,900 deaths in Spain due to the flu, according to the ISCIII. Vaccination coverage for those over 65 was 53.5%, a percentage similar to what is expected this season, pending final data, so in the current epidemic it is predictable similar mortality. Studies based on data from other years raise the number of deaths caused by flu epidemics in Spain to 6,000, reports Trilla.
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“Vaccination is the best way to prevent the flu”, highlights the WHO. Other ways to avoid contagion, according to the WHO, are: wash your hands regularly, since flu viruses are often transmitted when you touch your mouth, nose or eyes with your hands; cover your mouth and nose with a disposable handkerchief or the inside of your elbow, but not with your hand, when you cough or sneeze; stay at home if you feel unwell, and avoid contact with sick people if possible. The ECDC, for its part, recommends “wearing a mask in closed public spaces”, but warns that “it should be used correctly to obtain the desired effect”.
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The flu vaccine takes two weeks to induce effective protection, as the immune system needs these two weeks to produce the specific antibodies that will protect against the flu virus. If a person is vaccinated this week, they will not be protected during the period when the epidemic will reach the peak of infections and the risk of infection will be higher. Yes, it will be during the following weeks, when Spain will still be in an epidemic situation, although the infections will decrease.
An additional disadvantage of getting vaccinated now is that it can be difficult to get the vaccine at a time when primary care centers are strained by the influx of patients with respiratory infections.
