The information here is provided by courtesy of the Network's short online course - "An Introduction to Global Health".
A novel infection really means an infection that is new to a population.
Existing human infections transmitted from one population to another
In the past when there was little travel, an infection e.g. measles, influenza may have been common in one population but have never occurred in another population. The population where it had never occurred would have no immunity.
Explorers or traders from the country where the infection was common often took the disease with them. The people without immunity in the country to which they went would be overwhelmed by the new infection. Smallpox is another example that has decimated indigenous populations Australia and America in the past.
Infections that are new to humans
The reservoir for some infections may be in animals (zoonoses) and never reach humans until they encroach into areas where the animals live and there is spread from the animals to humans. Examples of these include
- HIV : The Human Immunodeficiency Virus, which is thought to have crossed the boundary to humans from members of the ape family in Africa.
- Ebola : From a virus which is transmitted to humans through contact with an infected bat of non-human primate in Africa.
- SARS : Severe Acute Respiratory Syndrome caused by a corona virus originating in bats in China.
- MERS : Middle East Respiratory Syndrome caused by a corona virus living in camels in the Middle East.
- COVID-19 : From a corona virus normally living in bats in China. It now has several variants.
The link below to video on You Tube summarises the relationship between SARS (SARS-CoV), MERS (MERS-CoV) and COVID-19 (SARS-COV-2)
Epidemics and Pandemics
Epidemic : An epidemic is an increase, often sudden, in the number of cases of a disease above what is normally expected in that population in that area.
Pandemic : A pandemic refers to an epidemic that has spread over several countries or continents usually affecting large number of people.
A highly infectious disease for which there is no cure is likely to spread rapidly and, with today’s travel patterns, is likely to spread worldwide very quickly unless it is contained. We knew before the COVID-19 pandemic that something like it was going to happen. The question was not “whether” but “when”. We can be pretty confident that another highly contagious organism will evolve or be transmitted to humans in the future.
Follow this link, if you would like to learn more about the definitions of sporadic cases, endemic and hyperendemic diseases, clusters, outbreaks, epidemics and pandemics.
Role of WHO
WHO develops global strategies for the prevention and control of epidemic-prone diseases, such as yellow fever, cholera and influenza. It has lead measures to prevent or control outbreaks of diseases such as
- Eliminating Yellow Fever Epidemics strategy 2017- 2026
- Ending Cholera: a Global Roadmap to 2030
- Pandemic Influenza Preparedness (PIP) Framework
- Global Strategy for Influenza 2018-2030
(See "Further Reading" to see these.)
Control or elimination of these is possible by the combination of a well organised public health infrastructure and the development of vaccines.
WHO is also the secretariat for the governance of global emergency stockpiles, including the International Coordinating Group on Vaccine Provision, which manages and coordinates the provision of emergency vaccine supplies and antibiotics to countries during major outbreaks.
More information about WHO activities in preventing epidemics and pandemics
WHO : Disease outbreaks
WHO: Eliminating Yellow Fever Strategy 2017 - 2026
WHO: Ending cholera : A Global Roadmap to 2030
WHO: Pandemic Influenza Preparedness (PIP) Framework
WHO: Global Influenza Strategy 2019 – 2030