Swine flu: the H1N1 virus and its new form G4

Swine flu: the H1N1 virus and its new form G4

In 2009, the swine flu terrified people around the world – after a very short time, it had leapt the Atlantic from the first cases and deaths in Mexico. Many people feared a catastrophe of international proportions. In the media, one horror story followed the other. In the summer of 2020, a new virus was discovered in China. What is behind the pathogen H1N1, and how dangerous is its newer mutation called G4?

What is swine flu?

Although the name swine flu (also swine influenza) may sound misleading initially, the disease affects not only pigs but also humans. The swine flu variant, known since 2009, is caused by a new, previously unknown flu virus.

Swine flu viruses are the type A influenza viruses known since the Spanish flu shortly after the First World War. The causative agent of the swine flu discovered in 2009 bears the designation A/California/7/2009 (H1N1).

Type A influenza viruses have numerous subtypes, designated H for haemagglutinin and N for neuraminidase, depending on the type of protein envelope. Most of these subtypes are harmless or only dangerous for animals; the subtype influenza A (H1N1) is responsible for humans’ “normal” flu.

It is typical for influenza viruses to change constantly, and the immune system no longer recognizes these mutationsThis is also why the flu vaccination must be repeated yearly.


Origin of swine flu: where does it come from?

The variant of the H1N1 subtype, commonly called swine flu, is a so-called reassortant (also called an “antigenic shift”). This sudden mutation occurs when two or more subtypes exchange their genetic material. Harmless viruses that are only dangerous for animals can suddenly become aggressive variants that can be transmitted in an unusual way and against which there is initially no immune protection. This is precisely what happened with the bird virus epidemic, for example.

Pigs are particularly predestined as “breeding grounds” for such mutations. This is because their immune system has receptors for the proteins (haemagglutinins) of different virus subtypes, so a cell can easily be infected with several viruses simultaneously.

There are different types of swine flu. The 2009 swine flu virus combines two strains of swine flu and one strain each of bird flu and human flu. The symptoms of swine flu are similar to those of other types of flu; the only distinguishing features are diarrhoea and vomiting.

G4 virus: Pandemic risk from other swine flu pathogens?

In the summer of 2020, the increased occurrence of a new swine flu virus in China became known. The spread of the new pathogen called  “genotype G4 reassortant Eurasian avian-like (EA) H1N1”  (G4 for short) was determined using nasal swabs from pigs.

Scientists collected over 30,000 samples from slaughterhouses in 10 Chinese provinces between 2011 and 2018. The study results were published in July 2020 in the Proceedings of the National Academy of Sciences of the United States of America (PNAS).

A total of 179 different swine flu pathogens were found. However, the G4 virus was found particularly frequently in the samples. According to the Chinese research team, G4 is highly infectious and capable of replicating in human cells.

In contrast to the SARS-CoV-2 coronavirus, which was probably also transmitted from animals to humans and then spread rapidly worldwide, G4 does not appear to be developing into the next swine flu pandemic, according to experts. So far, there have only been a few infected people in China, and there has not been any transmission from person to person. In addition, there is already a certain level of immune protection worldwide against the H1N1 virus type, to which G4 belongs. This is another way in which swine flu differs from the coronavirus.


When was the last swine flu in Germany?

The swine flu spread in Germany in 2009 but was relatively mild. Nevertheless, the World Health Organization (WHO) warned of a possible global epidemic (“pandemic”) this year – on June 11, 2009, it announced the highest safety level. Experts have classified the swine flu pathogen as a health risk of international importance, comparable to SARS in 2003.

But there were also voices from experts who advocated not overestimating the danger. Not only did the number of people who fell ill and died from swine flu fall relatively quickly, but they were far below the expected number of victims from the outset.

In August 2010, the WHO declared the swine flu pandemic over.

How dangerous is the pig flu?

Even if the variant of swine flu, which has existed since 2009, initially spread relentlessly, some experts did not consider it any more dangerous than the regular influenza virus at that time. The swine flu peaked around the turn of the year 2009/2010. At the beginning of 2011, swine flu was officially declared seasonal flu.

Experts disagree about the danger of swine flu: some scientists assume that the elderly, the sick and children are particularly at risk of suffering a severe course, even if it is striking that, compared to other variants of the flu, young, healthy adults are more likely to be infected with swine flu. Other experts, on the other hand, think that although the risk of infection is no greater than with the usual flu, there is a risk of death.

However, such assumptions contradict the absolute figures: while between 5,000 and 15,000 people die from seasonal flu in Germany yearly, the deaths from swine flu amount to 258 people out of 226,000 reported swine flu, according to the Robert Koch Institute (RKI). -Cases between fall 2009 and August 2010. A 2012 study estimated the number of deaths from swine flu in the first year to be between 151,700 and 575,400.

How is swine flu transmitted?

Swine flu infection occurs primarily from pig to pig and from pig to human.

In addition, this aggressive variant of swine flu can spread atypically from person to person. Because of this, such a disease can spread quickly in our globalized world. No wonder that only two to three weeks have passed between the first known cases in Mexico and the first occurrence in Germany during the 2009 pandemic.


How can you get infected with swine flu?

Swine flu symptoms appear after an incubation period of one to four days; it is contagious from the start of the incubation period. As with the common flu, infection with swine flu occurs primarily via droplets released into the air when you cough or sneeze.

Like the coronavirus, the risk of infection with swine flu is highest in closed, poorly ventilated rooms or close physical contact.

Contrary to popular belief, there is no risk of catching swine flu from eating pork.

Swine flu symptoms

The spectrum of manifestations of swine flu ranges from cases without symptoms to a fatal course. The common symptoms of swine flu, such as fever, cough, cold, and body aches, are comparable to typical flu symptoms.

This means that swine flu cannot be detected without further blood tests. In addition, other symptoms, such as vomiting and diarrhoea, can occur with swine flu. In addition, it is often atypical to regular flu since swine flu often begins with a fever before other symptoms appear.

The Robert Koch Institute evaluates the following signs as suspicious for swine flu: fever and at least two symptoms of an acute respiratory infection. This includes:

These symptoms are considered signs of swine flu, mainly when they occur in at least one of the following contexts:

  • after staying in an area defined as a risk of swine flu
  • After direct contact with a person who has probable or confirmed swine flu infection or has died from it
  • after being in a room with a confirmed human case(s) of swine flu at the same time (e.g. on an aeroplane)
  • at work in a lab testing samples for swine flu virus

Swine flu vaccination and other protective measures

Pigs can be vaccinated to prevent infection and further transmission of swine flu. In the autumn of 2009, a large-scale vaccination campaign against swine flu was also launched for humans – the first mass vaccination in over 40 years. At that time, the regular flu vaccination was ineffective against swine flu.

As with other vaccinations, temporary side effects such as nausea, flu-like symptoms, or joint and muscle pain have been observed with vaccination against swine flu. The active substance “Pandemrix”, used among other things for vaccination, was also suspected of triggering further vaccination damage in the form of severe allergic reactions or narcolepsy. The active ingredient is currently no longer used in Germany.

In the meantime, the “normal” flu vaccine also protects against swine flu. A vaccine against the new G4 virus does not yet exist.

Since the pathogen is transmitted via droplets, similar to the coronavirus pandemic when swine flu broke out in Mexico, more significant events were cancelled, schools were closed, and close physical contact was discouraged. However, these measures were not justified given the isolated occurrence of cases of illness, as in Germany.


Protective measures against viruses in general

To protect against swine flu or seasonal flu, however, there are some easy-to-follow hygiene rules that everyone should be familiar with, at least since the coronavirus pandemic.

According to the recommendations of the Robert Koch Institute, when there is a risk of viruses, care should be taken to ensure that no virus-contaminated secretions get into the respiratory tract:

  • Wash your hands frequently, especially after contact with people and if you have been in contact with objects touched by people who may have swine flu (such as doorknobs in public places). Also, wash your hands before eating and after sneezing or coughing into your hands.
  • Stay away from people who may be infected.
  • You should also stay home if you have the flu so as not to infect other people.
  • Cough into the crook of your arm instead of your hand.
  • Rarely touch your eyes, nose or mouth.

The fact that the G4 swine flu virus appeared at the same time as the coronavirus pandemic has the advantage that the population is already sensitized to these protective and hygiene measures. This point suggests that any spread of the new G4 virus could be contained quickly.

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