One of the oldest diseases, which still circulates in third world countries, is measles.
The first cases of measles were reported in the seventh century, and if a person is not vaccinated, the mortality rate is between 15 and 25 percent, according to the US Centers for Disease Control and Prevention (CDC).
Due to the length of the existence of measles, it is not possible to determine how many lives the disease has taken.
According to the World Health Organization website, measles (airborne) is the most contagious and between 92 and 95 percent of the population needed to be immunized, so that the remaining five to eight percent of the remaining can not get the disease.
Poliomyelitis, also a very dangerous disease, was observed in the 18th century and most commonly affects children aged three to eight years.
Before the vaccine appeared in the middle of the last century, the mortality rate was two to five percent in children, 15 to 30 percent in adults, and that percentage increased with brain complications to as much as 75 percent.
The WHO adds that the percentage needed to gain collective immunity to polio (transmitted via the oral-fecal route) is about 80 percent.
Measles or smallpox is probably the oldest disease in the world since it originated about 3,000 years ago in India.
WHO data show that, without vaccination, the mortality rate is 30%, and survivors often have permanent scars.
It is not known how many people died from the virus.
In order to neutralize measles (airborne and airborne droplets), 80 percent of people need to be immunized, according to WHO experts.
The pertussis vaccine was developed in 1926, but according to the US CDC, there are currently 24.1 million patients worldwide and 160,000 people die each year.
According to Harvard data, for whooping cough (transmitted by air and drops), 92-94 percent of the population needs to be immune to protect the rest.
Mumps is also a very old disease, first reported in the fifth century, and the death rate per 10,000 population is between 1.6 and 3.8 percent due to complications caused by inflammation of the brain.
Harvard data show that mumps, which is transmitted through air and droplets, requires 75 to 86 percent of the population to be immune, and the vaccine was developed in 1967.
In developed countries, the death rate from rubella virus (airborne and droplet transmission) is between 0.05 and 0.1 percent per 1,000 cases, significantly lower than in third world countries, where the death rate is between three and six percent.
The virus was registered in 1815, the vaccine was made in 1967, and it is estimated that between 83 and 85 percent of immunity creates collective immunity, according to Harvard data.
SARS was discovered in 2002 in China and was active until 2004 and is transmitted through air and droplets.
The WHO estimates that the death rate was around 11% when the epidemic ended, affecting four other countries besides China.
8,098 people became infected and 774 died when the WHO declared an end to the epidemic in July 2003, although there were several cases in the following years.
The vaccine does not yet exist, although the virus has mysteriously disappeared so far.
For SARS (airborne and airborne transmission) it is estimated that between 50 and 80 per cent of the population need to be immune to stop the spread.
As for Ebola (body fluids), which is the most dangerous of these viruses, the mortality rate is about 50 percent.
The first case was reported in the Congo in 1976, and it is estimated that over 80 percent of people need to be vaccinated to get immunity in a herd, however, that number is uncertain because it is not certain how long it can protect against Ebola. The US Food and Drug Administration (FDA) has approved the first vaccine in 2019.
In addition to Ebola, a great threat to humanity is the “cousin” Covid-19 – MERS.
MERS belongs to the group of coronaviruses, and the first case was registered in 2012 in Eden, Saudi Arabia, and the mortality rate was between 34 and 35 percent by January 2020, according to the WHO.
There were 858 deaths out of 2,519, and MERS is also called humpback camel disease, which transmitted the virus to humans.
It is still not entirely certain whether it is transmitted only by drops or there are other modes of transmission from person to person.
When it comes to covidium 19, one of the coronavirus viruses that is transmitted through the air and droplets, scientists still can not agree on the percentage of immunity necessary for the immunity of the herd, especially because it is a virus that returns after a few months and is still unknown to him.
So far, more than 1.5 million people have died from Covida 19, nearly 70 million cases have been infected worldwide, and in order to stop the spread, and scientists have not yet agreed, between 60 and 80 percent of people need immunity.
Collective immunity or “herd immunity” develops when most individuals in a community develop immunity to a disease that prevents the transmission of the disease, so that the whole community is protected, not just those who are immune to a particular disease.
In order to develop collective immunity, it is first necessary to spread the infection, to vaccinate people, so that there are different percentages of different diseases that need to occur in order to develop “herd immunity”.