Pig caution

The current outbreak is dangerous because viruses containing sequences from swine flu, avian flu and human flu are passed from person to person and not just through contact with pigs * The good part: the known flu drugs and vaccines can work against this virus

All over the world, the headlines are reporting an outbreak of an epidemic - Cases of swine flu have been discovered in Mexico, the USA, and Canada - By the time you read this, several more countries will surely have joined the list. Even in Israel there is a "suspected" patient who contracted swine flu. What is behind these scary headlines?

As of this writing (Sunday evening), hundreds of cases of the virus have been discovered in Mexico, and dozens have died from pneumonia that developed as a result of the disease. No deaths are known outside of Mexico. In the case of a new swine flu, the biggest concern is the transmission of the virus from person to person, and not just from infected pigs to humans who come in contact with them - so anyone who is near a person with this flu could become infected. Unfortunately, it seems that among the patients with the new virus there were those who did not come into direct contact with pigs - that is, the virus is apparently able to pass from person to person.

Another cause for concern is the severity of the disease it causes, and the fact that many of the patients who developed pneumonia were adults and relatively young - in contrast to the seasonal flu, which mainly endangers the elderly and children, who have weaker immune systems. This is reminiscent of the infamous Spanish flu virus, which killed approximately 50 million people between 1918 and 1919. This virus caused excessive and incorrect activation of the immune system, similar to an allergic reaction - a reaction that does not eliminate the virus, but is very harmful to the body. Due to this, it is precisely those with a strong immune system who get sick the most severely.

It should be noted that it is still not clear how far the virus has spread and what the mortality rate of the patients is - mainly because it is likely that only a small part of the patients with this particular virus were indeed identified as such. In addition, patients are known to respond well to certain anti-influenza drugs. The genetic sequence of the virus has been identified, and researchers at the US Centers for Disease Control have begun developing a vaccine against it - although this may take several weeks.

But perhaps one should also be careful of an overly rash response by the health services. In 1976, a panic similar to the one that exists now arose in the USA, also due to swine flu. About 500 cases were discovered at a military base in New Jersey, and one of the patients died. The panic caused about 40 million people in the US to be vaccinated, but this had severe side effects: several hundred people developed a neurological syndrome called Guillain-Barré, which can lead to temporary or permanent paralysis. To this day there is a debate as to whether such a widespread vaccination was necessary. We will never know, of course, whether an epidemic would have broken out if the vaccine had not been given.

To understand the current outbreak, you should first understand the structure and life cycle of the flu virus - they are what make it a virus that is so difficult to defend against. The flu virus is an RNA virus - that is, its genetic information is not encoded in a DNA molecule, like ours, but in a similar molecule, the RNA. The RNA is surrounded by a protein coat that protects it and allows it to enter the host cell. Like viruses, it is unable to reproduce itself, and it penetrates a cell - of a human or an animal - and uses the mechanisms of the host cell for this purpose.

The genome of the virus contains only 11 genes, including genes that code for two proteins used to identify the different substrains of the flu - hemagglutinin (HA) and neuraminidase (NA). The hemagglutinin is particularly important for the preparation of vaccines, since it is a protein that is on the surface of the virus and helps it bind to the cells it is about to infect - and thus it is exposed to detection by the immune system. Neuraminidase comes into action at a later stage - it is needed for the new copies of the virus to leave the infected cell and infect other cells.

The influenza virus has 3 main strains - A, B, and C. Influenza A is a severe and extremely common flu, and all known outbreaks of flu epidemics were caused by viruses of this strain. Its subspecies are characterized, as mentioned, by different types of the proteins meagglutinin and neuraminidase. For example, both the current swine flu virus, as well as the virus that caused the Spanish flu, belong to strain A and substrain H1N1 - which have type 1 hemagglutinin and type 1 neuraminidase.

What makes the influenza virus such a stealthy virus, that it is so difficult to develop a vaccine against it? Part of the answer can already be found in the names given to the recent outbreaks - swine flu and bird flu. Influenza viruses can indeed attack animals as well - in fact, seabirds are the natural surrogates of influenza A. Usually, viruses that infect one animal cannot infect another animal - but sometimes, the viruses can undergo mutations in poultry, pigs and animals -An additional life, which will make them - by chance - have the potential to infect humans, and possibly also pass from person to person. Thus, new viruses appear every few years, which have mutated in animals, and our immune system does not know how to deal with them. But the influenza virus has another surprise: besides mutations in the genetic sequence, which occur in all living things, the virus can change its shape in another way. Unlike most viruses, its genome does not consist of one continuous RNA segment, but of 8 different segments. This allows the virus to exchange entire segments of its genome with a flu virus of another subspecies - if both infect the same cell. Indeed, when the researchers examined the virus causing the current epidemic, they discovered that it is a hybrid of 4 different viruses: viruses of bird flu and swine flu from North America, Asian bird flu, and human flu. It is still unclear how exactly such a hybrid virus was created.

So are we in for the next big pandemic? Most likely not. Today, of course, we have much more tools to deal with such an epidemic, and as mentioned, there are drugs that are known to affect the virus. We will have to wait and see how the story will develop, and hope that the disease will stop quickly.