Over 200 cases of influenza in Poland this season and there are 75 thousand of them. weekly. Scientists have also noticed that a new, previously unknown strain of viruses is preparing for the attack.
Flu in Poland attacks. The number of cases has already exceeded 200, and according to the data of the National Institute of Public Health, at the beginning of February 2015 there were 75. sickness weekly.
According to the epidemiologist, prof. Andrzej Zieliński, this is not a situation that differs significantly from previous seasons. As prof. Zieliński, in the fall of last year, i.e. at the beginning of the flu season, there were more cases than in recent years. But then their number has decreased and is now increasing again. The forecasts of the American Center for Disease Control (CDC) mark the peak of the flu season in Central Europe, that is also in Poland, at the turn of February and March this year. so later than usual.
However, US researchers at the CDC also noted something disturbing: they believe this year’s flu vaccine is less effective than in previous seasons, especially in Europe and the US.
H3N8 in the US, will also be in Europe
Why is this happening? Scientists at the infectious disease Institute Pasteur in France say Europe and North America are being attacked by new strains of the flu virus not yet included in the vaccine. Their appearance was recorded on both sides of the Atlantic.
In the Bulgarian village of Konstantinovo, the Food Safety Agency (BFSA) detected at the end of January this year. an outbreak of the H7N9 virus, or avian flu, and a strain that is suspected of infecting humans – potentially capable of transmission from animals. Dr. Georgi Mitev, who is in charge of the BFSA, told the Bulgarian radio Focus that 21221 birds from 105 farms were slaughtered in Konstantinów.
All actions appropriate to the situation were taken. Unfortunately, it meant killing all the birds in the whole village, Mitev said. He added that the acquired H7N9 virus strains are currently being tested, and the Agency’s inspectors are checking for further avian flu outbreaks in the area. If the virus begins to expand, it will quickly reach the Balkans on the one hand and Central Europe on the other. In a devastated, war-ravaged Ukraine, the H7N9 epidemic could even mean a disaster.
The second bad news comes from the fall of 2014 and the American side of the Atlantic, specifically its coast closest to Europe – New England. Scientists from St. Jude Children’s Research Hospital examined common seals with an unknown disease. The first tests showed a viral disease. Sections taken from the lungs and upper respiratory tract revealed a new, so far poorly recognized, strain of avian influenza – H3N8.
The virus first caused an epidemic in New England seals, killing 160 animals in 2011. At that time, antibodies to this strain were discovered in individual fishermen, which was an alarm signal. However, it wasn’t until last year that it was revealed that H3N8 exhibits the same key protein mutation that was revealed in the highly pathogenic H5N1 strain of avian influenza.
The changes concern two mutations in the hemagglutinin (HA) protein and the PB2 gene. The HA protein is carried on the surface of the virus and allows it to attach to the attacked cell. A mutation in PB2 indicates increased virulence manifested by more severe disease symptoms. Simultaneous mutations in the HA protein and the PB2 gene were detected in 2012 in the H5N1 strain and they contributed to the fact that it acquired the ability of droplet transmission
H3N8 can therefore infect via the air. In vitro studies have proven that this is the case – the newly discovered strain grows in the cells of the lungs. Checking on ferrets revealed that this strain is as easily transmitted as seasonal flu viruses. Worse still, apart from individual cases, no immunity to this strain of influenza has been found in humans. It was checked on 102 people vaccinated in 2009-2011.
This means that there are new highly infectious strains of avian influenza virus other than the already known H5N1 and H7N9, said in Nature, research leader Dr Stacey Schultz-Cherry. It is worth noting that in cases of epidemics caused by these two strains, the death rate reached 60%. Perhaps H3N8 is not such a new strain, say CDC specialists, suspecting that it was this virus, which was transmitted through horses and dogs, that caused the great flu pandemic in the 1880s, killing tens of thousands of Americans and Europeans. According to researchers at Institute Pasteur, it is only a matter of weeks, or months, before H3N8 will arrive in Europe.
How the virus cheats
As it turns out, virulent strains of flu have hijacked another mechanism by which seasonal flu viruses trick the human immune system and vaccine-induced immunity. As a result of this mechanism, we have to vaccinate frequently and the vaccine contains the same flu strains.
An international research team, working under the leadership of Dr. Bjorn Koel from the Erasmus Medical Center in the Netherlands and prof. Derek Smith from the University of Cambridge, found during the research that in seasonal and epidemic viruses, the protein envelope changes in seven places. This is enough to trick the immune system. Until now, it was believed that such changes must occur in 130 areas on the surface of the shell.
The flu vaccine is made up of inactive flu viruses of the three most important types and epidemic viruses. In this way, the immune system becomes familiar with the individual strains. He recognizes viruses when he comes in contact with them and can deal with infections.
However, single amino acid changes occur in the surface protein envelope of seasonal influenza viruses every 2-3 years. As the researchers found, this amino acid exchange takes place at 7-8 sites, and this is enough to trick the immune system into ceasing to recognize the virus. All amino acid exchanges occur in the so-called binding site – the field where the virus adheres to the attacked cell. However, a virus with four amino acid changes in its protein envelope is sufficient to cause infection in immunocompromised people. Until now, it was believed that in order to completely deceive the human immune system, this replacement had to take place in 130 areas. According to WHO experts, this means that it is necessary to update at least twice a year the catalogs of the virus strains that will be included in the vaccine. The discovery of an international team is, however, a kind of warning sign – it means that you need to vaccinate, because even a vaccine with a weaker effect means that in the case of infection with a changed virus, the flu is easy to go through and it does not threaten with complications or even pose a threat to life. In the case of people with weakened immunity – older, young children – this is very important. Influenza also causes hospitalizations and deaths in Poland.
Tekst: Marek Mejssner