Emerging Infectious Diseases

Emerging infectious diseases are those due to newly identified and previously unknown infections which cause public health problems either locally or internationally”. In the past 20 years, at least 30 new diseases have emerged to threaten the health of hundreds of millions of people. Emerging Infectious Diseases have not occurred in humans before this type of emergence is difficult to establish and is probably rare. They have occurred previously but affected only small numbers of people in isolated places (Ebola hemorrhagic fever are examples); or have occurred throughout human history but have only recently been recognized as distinct diseases due to an infectious agent (Lyme disease and gastric ulcers are examples) (Table 1). 

Re-Emerging Infectious Diseases

Re-emerging infectious diseases are those due to the reappearance and increase of infections which are known, but had formerly fallen to levels so low that they were no longer considered a public health problem”. Re-emerging infectious diseases often appear in epidemic proportions. Re-Emerging Infectious Diseases are diseases that once were major health problems globally or in a particular country, and then declined dramatically, but are again becoming health problems for a significant proportion of the population. Many specialists in infectious diseases include re-emerging diseases as a subcategory of emerging diseases (Table 2). 

Responsible Factors

The factors responsible for emergence and re-emergence of infectious diseases are:

• Unplanned and under-planned urbanization

• Overcrowding and rapid population growth

• Changes in genetic makeup of the pathoge

• Poor sanitation

• Inadequate public health infrastructure;

• Resistance to antibiotics

• Increased exposure of humans to disease vectors and reservoirs of infection in nature

• Rapid and intense international travel

• Practice of modern medicine and relaxation in immunization practices

• Deforestation

• Failure to control carriers or breakdown in water and sanitation systems

• High risk human behaviour

• Channelling of funds to other problems

“Emerging and re-emerging infections reflect the constant struggle of microorganisms to survive” (Figure 1).

Table 1: Emerging Infectious Diseases

Table 2: Re-Emerging Infectious Diseases

Figure 1: Responsible Factors

Bacterial Infections, Viral Infections, Parasitic Infections and Fungal Infections

In an era of heightened pandemic vigilance, the profile, nature, and scope of emerging infectious diseases are varied and multiform. Subsequently, a range of infectious diseases, with the cited potential to transpire into significant public health emergencies, are presented within the following classifications of emerging and re-emerging infectious diseases: bacterial infections, viral infections, parasitic infections and fungal infections. (Figure 2-5).

Global Response

Establishment of the Division of Emerging and other Communicable Diseases Surveillance and Control (EMC), by WHO to Strengthen national and international capacity in the surveillance and control of communicable diseases, including those that represent new, emerging and re-emerging public health problems, for which it ensures a timely and effective response.

Role of WHO

The World Health Organization, as one of the partners in this global effort, is strengthening global monitoring systems to serve as part of the overall detection system. In addition to partnership in global monitoring, WHO is working in countries to strengthen national disease detection and response through improved surveillance systems, and specialized training in epidemic preparedness and response. A final role of WHO in this partnership is to help ensure a coordinated global response to infectious diseases of international importance, often with the technical expertise of the WHO Collaborating Centres or other centres of excellence.

WHO Collaborating Centres

The first global monitoring system is that of the WHO Collaborating Centres, specialized Laboratories and institutions with expertise in infectious disease diagnosis and epidemiology. Through WHONET and GASP, WHO regularly obtains standardized information of known quality on the current state of antimicrobial resistance. Helps countries use this information nationally for sound drug policies, and internationally uses the information to identify problems. Advocate research and development on antibiotics.

Figure 2: Emerging and Re-Emerging Bacteria

Figure 3: Emerging and Re-Emerging Virus

Figure 4: Emerging and Re-Emerging Parasites

Figure 5: Emerging and Re-Emerging Fungi [1]

International Health Regulations (IHR)

The third system is represented by the International Health Regulations (IHR), currently the only international public health legislation which requires mandatory reporting of infectious diseases. Three diseases are covered by the IHR – cholera, plague and yellow fever [2].

Steps Forward: Addressing Emerging and Re-emerging Diseases

The wake of the 2014 West Africa Ebola epidemic has reinvigorated and galvanized global efforts to monitor and regulate the emergence and re-emergence of pathogens with pandemic potential and to effectively address and contain infectious disease outbreaks to limit global contagion. While the past public health emergencies of the early twenty-first century (such as SARS, H1N1, and Ebola) represent diverse and varied health histories, key elements of pandemic preparedness and response – including increased spending and investment in health security, the bolstering of routine and timely disease surveillance systems, and continued investments and support for the development and deployment of vaccines to protect populations from infection and limit contagion – should continue to inform and guide both short- and longer-term initiatives to regulate the spread of emergent and re-emergent infectious diseases [3].

The governments all around the globe should emphasized coordinated global and regional leadership to formulate timely and proportionate responses to emergent disease threats, strategic and targeted spending and investment, the continued development of effective and widely available vaccines to counter disease outbreaks, as well as the utilization of broad and nuanced understandings of the correlated realities of health and disease, economy, politics, and society as imperatives in continued global health initiatives to regulate and contain emergent and re-emergent diseases [4].

1. “Emerging and Re-Emerging Diseases.” Annals of Community Health, https://www.annalsofcommunityhealth.in/ojs/index.php/AoCH/pages/view/emrem. Accessed June 2022.

2. Roberts, S.L. “Emerging and Re-Emerging Diseases.” The Palgrave Encyclopedia of Global Security Studies, edited by S. Romaniuk et al., Palgrave Macmillan, 2019.

3. Fauci, A.S. “Emerging and Reemerging Infectious Diseases: The Perpetual Challenge.” Academic Medicine, vol. 80, no. 12, December 2005, pp. 1079–1085.

4. “Emerging and Re-Emerging Infectious Diseases.” Europa, https://ec.europa.eu/info/research-and-innovation/research-area/health-research-and-innovation/emerging-and-reemerging-infectious-diseases_en. Accessed June 2022.