Swine flu struck fear into people around the globe in 2009 – in a very short time, it had made the leap across the Atlantic from the first cases of illness and death 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 form of the virus was discovered in China. What is really behind the H1N1 pathogen and how dangerous is its newer mutation called G4?
What is swine flu?
Although the name swine flu (also: swine influenza) can sound misleading at first, the disease affects not only pigs but also humans. The variant of swine flu, which has been known since 2009, is caused by a novel, previously unknown influenza virus. Swine flu viruses belong to the influenza virus type A, which has been known since the Spanish flu shortly after the First World War. The pathogen causing swine flu, which was discovered in 2009, is designated A/California/7/2009 (H1N1). Influenza virus type A has numerous subtypes, designated H for hemagglutinin and N for neuraminidase, depending on the type of protein coat. Most of these subtypes are harmless or dangerous only to animals; the influenza A (H1N1) subtype is responsible for “normal” influenza in humans. A typical feature of influenza viruses is that they are constantly changing, which means that these mutations are initially no longer recognized by the immune system. This is also the reason why the flu vaccination must be repeated annually.
Origin of swine flu: where does it come from?
The variant of the H1N1 subtype commonly referred to as swine flu is a so-called reassortant (also known as an “antigenic shift”). This is an abrupt mutation that occurs when two or more subtypes exchange their genetic material. This means that harmless viruses that are only dangerous to 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 exactly what happened, for example, in the bird virus epidemic. Pigs are particularly predestined as “breeding grounds” for such mutations. This is because their immune system has receptors for the proteins (hemagglutinins) of different virus subtypes, so a cell can be infected quite easily with several viruses at the same time. There are several types of swine flu. The 2009 swine flu virus combines two strains of swine flu and one strain each of avian flu and human flu. Thus, the symptoms of swine flu are also similar to the symptoms of other types of flu; only diarrhea and vomiting appear as distinguishing characteristics.
G4 virus: pandemic threat from another swine flu pathogen?
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 detected using nasal swabs from pigs. A team of scientists had collected over 30,000 corresponding samples at slaughterhouses in ten Chinese provinces between 2011 and 2018. The results of the study were published in July 2020 in the journal 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 particularly common in the samples. According to the Chinese research team, G4 is highly infectious and capable of replicating in human cells. However, unlike the SARS-CoV-2 coronavirus, which is also believed to have been transmitted from animals to humans and then spread rapidly around the world, G4 does not appear to be developing into the next swine flu pandemic, according to experts. So far, there are only a few infected people in China, and human-to-human transmission has not occurred. In addition, there is already a certain degree 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?
Swine flu spread to Germany in 2009, but was rather mild.Nevertheless, the World Health Organization (WHO) warned this year of a possible worldwide epidemic (“pandemic”) – it declared the highest safety level on June 11, 2009. Experts classified the swine flu pathogen as a health risk of international significance, comparable to the occurrence of SARS in 2003. But there were also voices of experts who pleaded not to overestimate the danger. Thus, not only did the numbers of people who fell ill and died from swine flu decline relatively quickly, 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 swine flu?
Although the variant of swine flu that had been around since 2009 initially spread relentlessly, it was already considered by some experts to be no more dangerous than the normal influenza virus at that time. Swine flu had reached the peak of its spread around the turn of the year 2009/2010. At the beginning of 2011, swine flu was officially declared a seasonal influenza. Experts disagree about the dangers of swine flu: Some scientists believe that the elderly, the sick and children are particularly at risk of suffering a serious course of the disease, even though it is striking that, compared to other variants of the flu, it is primarily young, healthy adults who are infected with swine flu. Other experts, however, argue that while the risk of infection is no greater than with ordinary flu, the risk of a fatal outcome is. Such assumptions, however, are at odds with the absolute numbers: While between 5,000 and 15,000 people die from seasonal flu in Germany each year, deaths from swine flu total 258 people out of 226,000 reported swine flu cases between fall 2009 and August 2010, according to the Robert Koch Institute (RKI). A 2012 study estimated the number of deaths attributable to swine flu in the first year at 151,700 to 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 take the actually atypical route of spread from person to person. Because of this, such a disease can spread rapidly in our globalized world. No wonder, then, that only two to three weeks passed between the first known cases in Mexico and the first appearance in Germany during the 2009 pandemic.
How can you contract swine flu?
Swine flu symptoms appear after an incubation period of one to four days; it is contagious from the beginning of the incubation period. As with common flu, infection with swine flu occurs primarily through droplets released into the air when coughing or sneezing. Similar to the coronavirus, the risk of infection with swine flu is therefore highest in closed, poorly ventilated rooms or in close physical contact. Contrary to initial popular belief, however, contracting swine flu by eating pork is not to be feared.
Symptoms of swine flu
The spectrum of swine flu manifestations ranges from cases with no signs of illness to a fatal course. The common symptoms of swine flu, such as fever, cough, cold signs, and aching limbs, are similar to symptoms of normal flu. That is, swine flu cannot be detected without further blood tests. In addition, however, swine flu may have other symptoms such as vomiting and diarrhea. Furthermore, it is often atypical to the normal flu, as swine flu often begins with a fever before other symptoms appear. The Robert Koch Institute rates the following signs as suspicious for swine flu: fever and at least two of the symptoms of an acute respiratory infection. These include:
- Rhinitis
- Stuffy nose
- Sore throat
- Cough
- Shortness of breath
These symptoms are considered signs of swine flu especially when they occur in at least one of the following contexts:
- After spending time in an area defined as a risk for swine flu.
- After direct contact with a person who has probable or confirmed swine flu infection or who has died from swine flu infection
- After being in a room with confirmed/human case(s) of swine flu at the same time (for example, on an airplane)
- When working in a laboratory where samples are tested for swine flu virus.
Swine flu vaccination and other protective measures
Pigs can be vaccinated to prevent infection and thus further transmission of swine flu. A major vaccination campaign – the first mass vaccination in more than 40 years – against swine flu was also launched for humans in the fall of 2009. At the time, the normal flu vaccine was ineffective against swine flu. As with other vaccines, temporary side effects such as nausea, flu-like symptoms or joint and muscle pain were experienced with the swine flu vaccine. The active ingredient “Pandemrix”, which was used among other things for vaccination, was also suspected of causing further vaccine 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 vaccination against the new G4 virus does not yet exist. Since the pathogen is transmitted via droplets, large events were canceled, schools were closed, and close physical contact was discouraged, similar to the measures taken during the Corona pandemic when swine flu broke out in Mexico. However, these measures were not justified when there were only isolated cases of the disease, as in Germany.
Protective measures against viruses in general
To protect against swine flu or even seasonal flu, however, there are some easy-to-follow hygiene rules that should be familiar to everyone at least since the Corona pandemic. According to recommendations of the Robert Koch Institute, in general, when there is a risk of viruses, care should be taken above all to prevent virus-laden secretions from entering the respiratory tract:
- Wash your hands frequently, especially after contact with people and if you have had contact with objects touched by people who may be infected with swine flu (for example, door handles in public). Also wash your hands before eating and after sneezing or coughing into your hands.
- Stay away from potentially infected people.
- Likewise, if you have the flu, stay home to avoid infecting other people.
- Cough into the crook of your arm instead of your hand.
- Touch your eyes, nose or mouth as rarely as possible.
The fact that the appearance of the swine flu virus G4 coincides with the coronavirus pandemic has the advantage that the population is already sensitized to these protective and hygienic measures anyway. This point suggests that any spread of the new G4 virus could be quickly contained.
