Anyone who has lost his or her spouse is a "widower or widow". "Orphan" is someone who has lost his parents. But there is no word used to describe the loss of a child. For centuries, unfortunately, it was "normal" to see your baby die from a disease. In Switzerland, in 1876 (the beginning of the statistics of deaths), about 200 babies out of 1000 died before they had completed the first year of life. Fortunately, infant mortality today is reduced to ca. 3.5 per 1000 decreased.
This spectacular progress is mainly due to the widespread use of vaccination, combined of course with hygiene and good nutrition. This is because when a population is vaccinated en masse against the pathogen (virus or bacterium) of a contagious disease, it benefits from herd immunity: even if one person is infected, the infection cannot spread because his environment is already immunized. As a result, people who cannot be vaccinated – especially newborns and people with weakened immune defenses – are also protected by the group's resistance. The vaccination rate at which this herd immunity can be achieved depends on the diseases: The more contagious a disease, the higher the vaccination rate must be. For example, it is 95% for measles and 70% for hepatitis B.
Epidemics change history
Since ancient times, civilizations have faced various outbreaks of epidemics, often lasting several years. Sadly, plague, cholera, smallpox and typhoid fever have gained fame in Europe. As companions of famines and wars and great colds, these contagious diseases have raged one after another – or together – appearing and disappearing over the centuries. The most important epidemic in Europe is the black plague, which took away 25 to 50% of the population between 1347 and 1352 and caused great changes in the economy, geopolitics and even religion.
After these historical epidemics, the people who survived the infection were immunized. Only small children could still be affected by the infectious diseases. As a result, measles, for example, is very often – but falsely – perceived as a childhood disease. The same is true for smallpox (also called "smallpox"). They are caused by a particularly contagious virus that has raged for a long time. But thanks to the major vaccination campaigns carried out worldwide from 1958 onward, smallpox was eradicated in 1979, allowing vaccination to be discontinued. Polio (poliomyelitis) or diphtheria, which primarily affect children under five years of age, are also now under control in most regions of the world. Even the very contagious measles no longer occurs in certain regions of the world where vaccination rates are adequate.
In Switzerland, cholera is in its 19th year. Cholera is most clearly remembered in the twentieth century. However, if we look at the number of people who fell ill and the number of deaths, cholera killed fewer people than tuberculosis or the Spanish flu of 1918, which caused the deaths of 21,000 people in Switzerland. 70% of them were between 20 and 49 years old.
Outbreak, epidemic, pandemic
There are actually three words that can be used to describe the extent of a contagion. "Outbreak" is used to describe the sudden appearance of some cases. "Epidemic" is spoken of when a region or some countries are affected by the contagion. And one speaks of a "pandemic" when the wave of disease spreads to one or more continents.
An epidemic or pandemic can be caused by an already known bacterium or virus, if there is no protection by herd immunity (anymore) due to the proportion of vaccinated people. It can also be due to an emerging bacterium or virus, such as AIDS in 1983 or the coronavirus SARS in 2002 to 2004.
Seasonal flu is a contagious disease caused by multiple viral strains. Certain strains appear regularly by mutation or crossbreeding. Thus create new threats to the population. The aim of flu vaccines is therefore to immunize the population simultaneously against several strains: already known viruses and new mutants. It is the latter that specialists fear most, because they can trigger a new murderous pandemic, as they did in 1918, 1957, 1968 and 2009.
Four families of epidemics
Epidemic diseases can be divided into four families:
– Diseases of the digestive system: diarrhea, cholera, salmonella, etc. They are transmitted primarily through water contaminated with fecal germs. – Diseases whose pathogens are transmitted by droplets produced by coughing and sneezing: diphtheria, influenza, measles, tuberculosis etc. Infection occurs through inhalation of the infected droplets that are suspended in the air or have settled on food or objects. – Sexually transmitted diseases: AIDS, syphilis, hepatitis B, human papillomavirus, etc. – Diseases transmitted by bites or stings of animals (fleas, mosquitoes, ticks, mosquitoes): Malaria, yellow fever, dengue fever, Zika.
False sense of security
Knowledge of available medicines can lead to the feeling of being protected from major epidemics that have overshadowed people's lives in the past. But this is a mistake: mass mortality is possible at any time. Incessant movement of goods. People across the planet actually increase the risk. This is all the more true because too many people neglect their own vaccination protection or the vaccination protection of their children. You feel safe because the others are getting vaccinated: The vaccination rate then falls below the threshold that ensures herd immunity… This is why several major whooping cough (1994/1995) and measles (2006 to 2009) epidemics have occurred in Switzerland in recent decades – diseases that could actually remain contained.
Vaccines for individual protection
Vaccines not only help control or even eradicate serious contagious diseases. They also protect the individual against non-contagious diseases such as tetanus or tick-borne meningoencephalitis. In these cases, herd immunity is irrelevant: such a disease can be contracted even if all people in one's environment are well immunized.