Plagues and pandemics are no longer distant thoughts of the past. Previously referred as moments in history, infectious diseases have re-emerged as potential existential threats to mankind. International Health Security researchers have repeatedly warned society about impending pandemics and in 2020, the world experienced its first major pandemic in over a century. The SARS-CoV-2/COVID-19 pandemic came fast and hit hard, impacting the entire world within months of discovery. Although SARS-CoV-2 was a completely novel virus, there are an assortment of novel and timeworn pathogens fostering the potential to become the next pandemic. This chapter focuses on pathogens ranging from yeast to virus, capable of transmission through food, water, air, or animal, that could emerge as the next International Health Security threat.
- vector-borne diseases
- airborne diseases
- waterborne diseases
- foodborne diseases
- public health
- infectious diseases
- International Health Security
The current COVID-19 pandemic has given the world a new lesson that the war against human pathogens is not over. The next plagues are coming, that is for sure, we just do not know when and where they will emerge. The transcontinental global movement of human populations, animals, products, and food in unprecedented numbers and at immeasurable speeds has determined the emergence of new plagues. The International Health Security panorama is changing with the incorporation of vast geographical areas to the agroindustry; the displacement of large population groups either due to problems of floods, drought, wars, or people that search for better living conditions. In addition, the disposal of biological waste and the weaponization of pathogenic microorganisms are phenomena with serious consequences. International multinational cooperation is needed to improve the development and availability of drugs and vaccines at a global level, as well as, improving preventive health services, keeping safe all repositories of infectious agents, and the establishment of an International Health Security System focused on Infectious Disease Surveillance and Control.
An organized, systematic, four-step methodology for collecting key information was carried out to write this chapter. In a first step a search in websites such as the World Health Organization (WHO), the Centers for Disease Control and Prevention (CDC), and the National Institutes of Health (NIH) was conducted to identify emerging infectious diseases pathogens. In a second step, the main emerging infectious diseases pathogens were classified in viruses, bacteria, parasites and fungi as well as by their mechanism of transmission. In a third step, all updated manuscripts related with each one the selected pathogens were extracted from scientific databases including Pubmed, MEDLINE, Google Scholar, and SCOPUS. Finally, all pathogens were classified using the WHO Pandemic Phase Descriptions and Main Actions by Phase .
3. Pathogens to study
Vector-borne diseases are transmitted, either biologically or mechanically, via insect vectors or animal vectors. Vector-borne diseases were the cause of great plagues in the previous centuries and continue to take human lives every year. Although the invention of pesticides, better hygiene and sanitation, and improved physical barriers have contributed to the decreased incidence of these type of infections, globalization, deforestation, and global warming are causing Vector-borne diseases to experience a comeback . With enough conditions in their favor, Vector-borne diseases are capable to expand from being endemic in some areas to becoming a pandemic. Vectors range from insects to mammals and are present in all parts of the world. The pathogens described in this section are transmitted by mosquitoes, ticks, rodents, lice, and fleas.
An important factor regarding Vector-borne diseases and their respective vectors compared to other mechanisms of infectious disease transmission (e.g., airborne, foodborne) is the emerging data indicating vectors are capable of hosting more than one pathogen at a time [3, 4, 5, 6, 7]. Co-transmission and co-infection are not well understood yet are raising questions regarding clinical manifestation, virulence, and possible future implications. Although the mechanisms of co-infections are not well comprehended, there are documented case reports with individuals presenting more than one Vector-borne disease at the same time [8, 9, 10]. Specifically, there is rising concern about mosquitoes and their capability to co-infect humans, with recent studies showing
18.104.22.168 Yellow fever virus
Yellow fever (YF), one of the deadliest infectious diseases less than a century ago , was historically a neglected infectious disease unit the 1902 creation of the Pan American Health Organization (PAHO) and International Sanitary Bureau of the American Republics . Yellow fever is caused by the etiological agent yellow fever virus (YFV), belongs to the flavivirus genus and, is a part of the arboviruses group (i.e., a commonly used, yet unofficial, name for viruses transmitted by arthropods). . YFV circulates between humans, non-human primates, and several species of mosquito vectors (
22.214.171.124 Dengue virus
Dengue virus (DENV) occurs in over 100 countries causing nearly 100 million acute infections and half a million deaths each year [26, 27]. The disease itself is characterized by an acute fever which is transmitted from mosquitos (
126.96.36.199 Zika virus
One of the most famous infectious diseases of recent decades, Zika came into the international spotlight during its 2015 epidemic. Although Zika virus (ZIKV) was discovered in a Ugandan forest over 50 years ago, in 2015 it emerged as a global epidemic affecting multiple countries and causing widespread panic . In 2016, the World Health Organization (WHO) declared the outbreak as a Public Health Emergency of International Concern, with ZIKV affecting throughout the Americas and Caribbean. One of the main reasons for the declaration and widespread worry is the increase in microcephaly cases and other neurological disorders that ZIKV brought with it. Interestingly, prior to the outbreaks in the recent decade, ZIKV infections were considered benign . It was the increase in neurological disorders such as Guillain-Barré syndrome in older children and adults and microcephaly and other birth defects in newborns in the 2015 Brazil outbreak that forewarned the local and international community of the potential adverse effects from a ZIKV infection . Although the incidence of Zika cases has decreased since the 2015–2016 epidemic, a substantial amount of Zika research continues to provide new data and information on this infectious disease. Current research suggest Zika will be around until the foreseeable future with research indicating ZIKV actually circulates in areas previously unknown. Moreover, in 2019 Europe’s first autochthonous case  was identified and further confirmed the importance of vector control and public health programs. Like the flaviviruses mentioned above, ZIKV’s main vectors are
188.8.131.52 West Nile Virus
An emerging zoonotic arbovirus, West Nile Virus (WNV), was first described in a sick woman located in the West Nile Uganda district in 1937 . Sixteen years later WNV was detected in birds living in the Nile delta region, suggesting its transmission cycle involves mosquito vectors and birds – yet may infect humans . It is now known WNV is capable of infecting both humans and other vertebrate species, with its sylvatic cycle infecting horses and humans as dead-end hosts and birds as the amplifying host. Unlike the previously mentioned viruses, WNV uses the
184.108.40.206 Crimean-Congo hemorrhagic fever virus
A Nairovirus, Crimean-Congo hemorrhagic fever (CCHF), is an emerging infectious disease using
220.127.116.11 Mayaro virus
This emerging zoonotic pathogen is an enveloped +ssRNA virus belonging to the alphavirus genus of Togaviridae family . Mayaro virus (MAYV) is part of the viruses of Semliki forest antigenic complex and causes Mayaro fever [46, 47]. Transmission of MAYV into humans occurs primarily through the bites of infected mosquitoes of the genus
18.104.22.168 Chikungunya virus
First reported in 1952 in Tanzania, Chikungunya virus (CHIKV) is an alpha virus apart of the Togoviridae family and transmitted by Aedes mosquitoes . The word Chikungunya translates as “the disease that bends up the joints”, which is one of the severe symptoms of the disease (i.e., arthritis) . The main transmission among humans occurs through epizootic cycles, where vertebrates are the viral reservoirs and the mosquito acts as the vector . Since its discovery, there were CHIKV outbreaks throughout Europe, India, and Asia. CHIKV was a mostly a forgotten infectious disease until its 2006 resurgence and widened global reach. In 2007, Europe reported its first autochthonous CHIKV infection and by 2013 it had found the Americas, first landing in Saint Martin and then spreading throughout South America . In spite of underreporting and misdiagnoses cases have occurred in more than 45 countries . Active outbreaks allow humans to become the reservoirs and continue to fuel the outbreak. Like Zika, the first autochthonous cases in the Americas were fairly recent, with CHIKV’s first outbreak in the Northern and Northeastern regions of Brazil . The most serious outbreak was probably the Reunion Island outbreak between 2005 and 2006, where nearly a third of the island’s population (255,000) was infected and over 250 individuals died . A CHIKV infection typically causes symptoms such as fever, arthralgia, myalgias, and skin rashes . In a subset of cases, joint inflammation and arthritis lasting up to 4 months may occur . The increased incidence of CHIKV over the recent decades in areas previously unaffected, in addition to the wide geographical range of its vector (i.e., the Aedes genus) lead to heightened concern of future outbreaks and adverse health outcomes. Moreover, recently CHIKV infection is associated with abortion during the first and last trimesters of pregnancy, further emphasizing the need for CHIKV research and therapeutics .
As one of oldest infectious diseases known to mankind, Typhus, caused by the bacteria
Perhaps the most infamous infectious disease, the Black Plague or Black Death, is caused by
The causative agent of tularemia,
A newly uncovered bacterium,
In the last century, some of the deadliest pandemics were spread through respiratory droplets or aerosols. Globalization and shortening of travel time have further increased the speed of spread of airborne diseases. Scientific advances in vaccine development and antimicrobials has helped to counter these outbreaks however risk of massive outbreaks due to emerging and re-emerging pathogens remain and is an International Health Security issue. The 2019 coronavirus disease (COVID-19) pandemic has shown the susceptibility of human population to novel emerging or re-emerging pathogens and its significant effect on economic, social, and human health. It has also shown the ability of a pathogen to rapidly disseminate through airborne or respiratory route and the difficulties associated with prevention and control measures. The majority of pathogens require isolation, quarantine and respiratory precautions (surgical masks, personal protective equipment in hospitals, cleaning of surfaces, disinfection of surfaces, and hand hygiene) as prevention and control measures. Dangerous pathogens such as viruses, bacteria, or fungi transmitted from environment, animals or humans through respiratory route and having potential to cause epidemics and/or global pandemics are listed below along with the available medical countermeasures.
22.214.171.124 Variola virus
The variola virus is recognized as a huge threat to human health if used as bioweapon. This was based on the ability of Soviet Union to weaponize smallpox in the 1980s . In 1994, the WHO Committee on orthopoxviruses decided, the stocks of variola virus DNA should be kept at only two international laboratories in world, namely Centers for Disease Control and Prevention (United States) and State Research Center of Virology and Biotechnology -VECTOR institute (Russia) . However, fear remains that secret variola virus stocks could be kept illegally somewhere and be used in bioterrorist attacks; therefore, it is a threat for the International Health Security . Genomic studies on orthopoxviruses has suggested the deletion of genes as an important concept for the reductive evolution of orthopoxviruses in adapting to new host species or emergence of new virus species [83, 85]. The existence of zoonotic orthopoxviruses with the ability to cause sporadic human cases raises the possibility of reemergence of variola virus as part of these natural evolution of orthopoxviruses . Like the introduction of the smallpox in the Americas, either the release of variola virus intentionally or its reemergence as part of natural evolution can result in public health emergency of global concern with high fatality. This concern is mainly due to a huge proportion of the world being immunologically naïve, increased percentage of immunologically suppressed population, and globalization resulting in rapid spread of virus . The effective vaccine and two antiviral drugs (brincidofovir and tecovirimat) are available pharmaceutical measures to fight any future outbreak due to either natural evolution or bioterrorist attack . However, the lack of practical knowledge among healthcare professionals related to smallpox clinical characteristics may further delay early diagnosis, treatment and control of the outbreak.
126.96.36.199 Monkeypox virus
Monkeypox virus, has emerged as the most common pathogenic Orthopoxvirus and causes a zoonotic disease Monkeypox . Similar to the variola virus, transmission is through respiratory droplets/secretions or contact with the lesion material . Monkeypox is endemic in Central and West Africa with similar clinical manifestations as smallpox and a case-fatality rate of 10% [83, 84]. The clinical manifestations include fever, myalgia, exhaustion followed by appearance of rash and lymphadenopathy in 1–3 days [86, 87]. Monkeypox virus can infect a wide range of mammalian species with various species of African rodents acting as natural reservoir . Monkeypox virus usually results in sporadic cases due to low efficiency of person-to-person transmission and occurs mainly from primary human cases but never from secondary cases [83, 84, 86]. However, during the recent outbreaks in Nigeria and Democratic republic of Congo (DRC), increased person-to-person transmission was observed along with associated imported cases in UK, US, Israel and Singapore [83, 89]. Additionally, in the US Midwest outbreak, the virus showed the ability to infect intermediate hosts (prairie dogs) from natural reservoirs and subsequently infect humans . Infection with a Orthopoxvirus or smallpox vaccination provided protection against monkeypox virus and thus smallpox eradication and cessation of vaccination has resulted in decreasing number of vaccinated individuals . Currently the monkeypox virus is in stage-3 of pathogen evolution to cause disease and phase-3 of WHO pandemic security alert level. The risk factors of absence of population-scale immunity, increasing efficiency of person-to-person transmission, and the presence of animal reservoir along with potential intermediate host suggests that monkeypox is no longer a rare disease and has potential to cause widespread epidemics becoming a threat for International Health Security. There is currently no approved antiviral or detailed case management for monkeypox however, selective agents developed for smallpox virus could be tested for treatment efficacy in case of outbreaks .
188.8.131.52 Nipah virus
Nipah virus is an emerging zoonotic -ssRNA virus belonging to the Henipavirus genus and Paramyxoviridae family. The natural reservoirs of Nipah virus are the Pteropid bats (fruit bats) with pigs acting as intermediate hosts [91, 92]. The fruits bats are limited to farms and orchards in the tropical and subtropical regions of Asia, East Africa, and Australian continents [91, 92]. The consumption of fruits by pigs which are contaminated or partially eaten by the Nipah virus infected Pteropod bats results in the spillover of the virus to intermediate hosts . The transmission of the virus from intermediate hosts to humans is through direct contact with the excretions and secretions of infected pigs such as urine, saliva and respiratory secretions [92, 93]. The animal to human route is the primary mode of transmission with limited person-to-person transmission through direct contact with respiratory droplets or fomites. The major clinical manifestation of Nipah virus infection is acute encephalitis with headache, fever, vomiting, and dyspnea .
The Nipah virus outbreaks are limited to Asian continent with Malaysia (43%), Bangladesh (42%), and India (15%) reporting the incident cases worldwide . The first outbreak of Nipah virus was identified in Malaysia in 1998 which spread to Singapore in 1999. This was mainly due to the importation of infected pigs from Malaysia to Singapore and the spillover of infection among pig farmers and abattoir workers . This was followed by outbreak in Bangladesh in 2001 and neighboring India. In Bangladesh cases are identified nearly every year while India has reported outbreaks in 2001, 2007, and 2018 [92, 93]. All the Nipah virus outbreaks reported till now had limited person-to-person transmission with R0 < 1 . However, due to the high rate of mutations in the RNA virus, it has the potential of generating a strain with R0 > 1 . Currently the disease is in the stage-3 of pathogenic evolution with phase-3 on pandemic alert scale. There is currently no medical countermeasure (antiviral or vaccine) approved or available against Nipah virus . The genomic heterogeneity combined with the known susceptibility in humans and ability to cause person-to-person transmission suggests a future pandemic risk of Nipah virus and thus the listing of Nipah virus diseases as one of the WHO priority diseases with greatest danger for International Health Security [93, 95].
184.108.40.206 Hendra virus
Similar to the Nipah virus, Hendra virus is an emerging zoonotic pathogen belonging to the genus Henipavirus and family Paramyxoviridae. The Pteropid bats (Australian flying foxes) are the natural host with horses acting as amplifying hosts [91, 96]. Human disease follows transmission through contact with respiratory secretions of infected hosts while no person-to-person has been documented until now . The clinical feature of Hendra virus disease in humans is acute encephalitis with or without influenza-like illness . The first outbreak was identified in 1994 in Australia and the disease has been limited to Australia. There have been 7 human cases until now with a high case-fatality rate of 57% . Currently, the disease is limited to stage-2 of evolution with phase-2 of pandemic alert level. There is currently no medical countermeasure (antiviral or human vaccine) approved against Hendra virus; however. an equine subunit vaccine is approved in Australia [92, 96]. The identification of virus in horses and presence in Pteropid bats underpins the potential of virus to cause large outbreaks in future becoming a threat for International Health Security.
220.127.116.11 Influenza viruses
These are a group of four types of enveloped -ssRNA Influenza viruses (A, B, C and D) belonging to the Orthomyxoviridae family of virus and are the common etiologic agent of respiratory infections in humans . The virus is transmitted from person-to-person through respiratory droplets or contact with fomites . Of the four types of influenza viruses, Influenza A and B cause disease in humans with influenza A having the ability to infect hosts of multiple species (pigs, horses, aquatic birds and poultry) in addition to humans [68, 98]. Influenza A undergoes antigenic drift and antigenic shift and thus causes seasonal epidemics and global pandemics while Influenza B undergoes only antigenic drift and is responsible for only seasonal epidemics [68, 99]. Antigenic drift is due to point mutation and results in minor genomic changes while antigenic shift is due to genetic reassortment and results in major genomic changes . The antigenically different 18 hemagglutinin and 11 neuraminidase proteins further divides influenza A viruses into various subtypes i.e. H1N1, H3N2, H5N1, H7N9, H5N8.
Influenza A viruses have caused the highest number of known global pandemics in human history with Spanish flu (H1N1) in 1918, Asian influenza (H2N2) in 1957, Hong Kong influenza (H3N2) in 1968, and Swine flu (H1N1) in 2009 . The seasonal influenza is responsible for annual epidemics in the human population with approximately 5–15% of the total world population being affected annually . The clinical features of influenza infection include myalgia, headache, fever, sore throat, and non-productive cough with nearly 50% of infections asymptomatic . The worldwide dissemination of avian influenza A viruses in domestic poultry flocks and birds and the demonstrated ability to infect humans has raised the potential of future pandemic due to avian influenza A viruses which is of main International Health Security concern . In 1997, an outbreak of H5N1 in Hong Kong resulted in 18 human cases and resulted in six deaths . This was followed by continuous circulation of H5N1 strain in China with the widespread geographical distribution of this epizootic strain. Between 2003 and 2009, H5N1 resulted in 4o3 human cases with a high case fatality rate of 63%. Despite the high fatality, biological barriers prevent efficient binging of influenza virus to human receptors and thus the virus continues to have inefficient person-to-person transmission . Similar human infections resulting in small outbreaks have been seen in H5N8 and H7N9 strains of avian influenza A viruses [101, 102]. However, the high propensity of influenza virus to undergo mutational changes may result in a complete species switch and lead to a pandemic which becomes an International Health Security threat.
M2 proton channel inhibitors (amantadine and rimantadine) and neuraminidase inhibitors (oseltamivir, zanamivir, peramivir) are the traditional antiviral drugs approved for influenza prevention and treatment . All the influenza A viruses are resistant to M2 proton channel inhibitors making the neuraminidase inhibitors the drugs of choice against influenza viruses. Balovir Marboxil, a viral replication inhibitor was approved by FDA in 2018 but rapid emergence of resistance has prevented its routine use . The seasonal influenza inactivated vaccine requires yearly evaluation due to genomic heterogeneity and is effective mainly against the vaccine strains . Thus, the antigenic shift that results in emergence of pandemic strain would make seasonal vaccines ineffective. Currently, the influenza A virus are in different stages of pathogenic evolution ranging from stage-2, stage-3 or stage-5 and have a phase-3 or phase-5 pandemic alert level depending on serotype [68, 101]. The ability of influenza virus to infect multiple species, cross species barrier, and high genomic variability resulting in novel viruses with low immunity among the population are the reasons behind the constant threat of pandemic by influenza A viruses.
In 2019, a novel zoonotic beta-coronavirus (+ssRNA) emerged as the cause of viral pneumonia in Wuhan, China and was later named as
The first of the beta-coronavirus (+ssRNA) to emerge in Guangdong Province, China by zoonotic transmission was called Severe Acute Respiratory Syndrome-related Coronavirus (SARS-CoV) and was responsible for the 2002/2003 Severe Acute Respiratory Syndrome (SARS) outbreak [68, 104]. The SARS-CoV-1 causes symptoms similar to SARS-CoV-2. The main mammalian reservoir host of this virus were bats with Asian civet cat believed be to the source of initial human infection . The person-to-person transmission occurred due to contact with respiratory droplets or fomites. The epidemic started in November 2002 and spread rapidly to 29 countries in 5 continents resulting in 8437 cases and 813 deaths . The outbreak was contained in July 2003 and since 2004 no cases of SARS has been reported . Currently, there is no known transmission of SARS-CoV-1 to humans (stage-1) and it has a phase-1 pandemic alert level.
In 2012, a novel beta-coronavirus was identified to be the causative agent for acute respiratory disease in humans in Saudi Arabia and was named Middle East Respiratory Syndrome-related coronavirus (MERS-CoV) [104, 112]. Bats are the main mammalian reservoir for MERS-CoV with dromedary camels as the source of human infection [104, 112]. This enveloped +ssRNA virus is transmitted from animals to human through close contact with infected dromedary camels and/or person-to-person through respiratory droplets [104, 112]. The majority of cases of MERS-CoV are limited to Middle East with the lack of rapid global spread due to poor efficiency of person-to-person transmission . MERS-CoV infection results in symptoms similar to other beta-coronaviruses and range from mild influenza like illness to severe disease with respiratory distress, septic shock, and multi-organ failure . The initial case in 2012 was followed by an outbreak in Middle East in 2014 impacting 27 countries in Europe, Asia, Middle East, and North America with cases related to Middle East travel history . The associated Korean outbreak in 2015 was precipitated due to a super spreader event with the individual having travel history to Middle Eastern countries [104, 112]. Till December 2019, a total of 2499 confirmed cases and 858 deaths have been reported due to MERS-CoV . Research studies have shown the natural susceptibility among Alpacas and Llamas camelids to MERS-CoV [113, 114]. This raises the potential of widening of the geographic distribution of MERS-CoV to the South American region with high new world camelids population (Peru, Argentina, Chile, Bolivia) if the virus is introduced to these regions, becoming a threat for International Health Security in the Americas. Currently, the virus in stage-3 of pathogenic evolution and phase-3 of pandemic alert level. The lack of vaccine or treatment along with the potential for viral mutation that could increase zoonotic and/or person-to-person transmission may increase the epidemic potential of MERS-CoV and cause an International Health Security threat.
Different than any previously mentioned pathogens, Hantaviruses are an entire genus capable of causing human diseases. In 1981, this group of -ssRNA viruses were introduced into the Bunyaviridae family . Before 1993, Hantaviruses were thought to be solely responsible to cause hemorrhagic fever with renal syndrome (HRFS) in old world . The main reservoirs for this type of viruses are rodents such as Cricetidae and Muridae. In 1993, the first new world Hantavirus was found in the Southwestern region of the US. This virus would later be named Sin Nombre virus (SNV) and be known to cause hantavirus cardiopulmonary syndrome (HPS) . Since the discovery of SNV, the hantavirus genus includes more than 20 species and 30 genotypes . Scientists have identified the deer mouse as the major host of SNV with cases confirmed in at least 30 US states . The transmission of virus in humans is predominantly through inhalation of aerosolized rodent urine or salivary droppings. The pulmonary syndrome presents flu-like symptom lasting 3 to 5 days and after 7 days the cardiopulmonary phase may begin [115, 116]. Unfortunately, diagnosis of HPS has proved difficult and leads to misdiagnosis and underreporting . Currently, the SNV has a high case fatality rate of 35% with no licensed antivirals or vaccine. Since close contact with or among rodents account for majority of exposures, rodent prevention and population surveillance is essential for transmission control. In 1996, a study found evidence of person-to-person transmission of another hantavirus in Argentine, raising concern of larger outbreaks in future . Luckily person-to-person transmission is rare, if non-existent suggesting pathogen is in stage-2 of pathogenic evolution and thus, phase-2 of pandemic alert level. Yet, recent outbreaks of other Hantaviruses (e.g., Andes virus) are an alarm for International Health Security surveillance systems who worry about future local outbreaks or global pandemics due to potential for person-to-person transmission.
This gram-negative bacillus is commonly found in environment and is the etiologic agent of a serious disease “Melioidosis” in humans and animals . The agent was first identified in 1911 in Burma but was named
This gram-positive spore forming bacilli is the causative agent of anthrax, a zoonotic disease which is rare in humans and common in animals. Human anthrax is a highly contagious disease and can be transmitted from animals to human through contact with infected animal or animal products or ingestion of animal meat. However, this highly virulent disease has no documented person-to-person transmission [68, 130]. Herbivores animals are the primary reservoir of anthrax with all warm blood animals susceptible to
Worldwide approximately 20,000–100,000 cases of anthrax are reported annually, with the disease a major threat in arid regions of Central Asia, Africa, Middle East, Haiti, and South America [68, 131]. In the US, a total of 18 cases of inhalational anthrax and no case of gastrointestinal anthrax has been reported in the 20th century . The largest outbreak of human anthrax was reported in Soviet Union in 1979, due to ingestion or contact with contaminated meat. The spores of the bacilli are resistant to environmental conditions such as drying, heating, ultraviolet (UV) rays, and gamma radiation and can survive for decades [68, 130]. This makes
Tuberculosis (TB) is a chronic inflammatory disease caused by an acid-fast bacilli
TB affects all regions of the world with nearly a quarter of the world’s population infected with
One unique feature that differentiates
The lack of knowledge related to any animal reservoir makes the
Since ancient times, large number of pathogens (viruses, bacteria, parasites, fungi) found in the environment are responsible for causing severe morbidity and mortality. These pathogenic organisms mainly infect humans through respiratory droplets, aerosols, dust, vector bite, contaminated food or water, or direct contact with animal hosts. The emergence of SARS-CoV-2 in 2019 and its global spread resulted in the announcement of the sixth public health emergency of international concern in last 10 years after Influenza A (H1N1) in 2009, Ebola virus in 2014, Polio in 2014, Zika virus in 2016, and Ebola in 2019 . Moreover, in the last 20 years the emergence of novel pathogens such as SARS-CoV-1, MERS-CoV, Candida auris, and drug resistant bacteria in addition to the ongoing epidemics/local outbreaks of vector-borne diseases such as Crimean-Congo Hemorrhagic fever and Zika has raised International Health Security alarms. This chapter mainly concentrates on the epidemiology, pharmaceutical tools, prevention, and control of pathogens having respiratory or vector mediated transmission. Infectious diseases continue to be major causes of fatality worldwide despite the significant advances in civilization, scientific technology, and medicine. On the contrary, these same advances may contribute to the emergence, re-emergence, and rapid spread of diseases due to climate change, deforestation, globalization, and over usage of pharmaceutical tools. In the last few decades, the rapid emergence/re-emergence of novel and resistant pathogens make it essential to establish surveillance and research programs into potential pandemic causing pathogens. It is important to take cognizance of the hazards posted by these vector-borne and airborne pathogens, already circulating among the animal or human population to prevent the risk of epidemics and global pandemics. Majority of the viruses with potential to cause pandemics lack antivirals and vaccines while fungi and bacteria have developed resistance to antimicrobials. Thus, special attention needs to be paid in the research and identification of effective drugs against these pathogens to have the medical countermeasures available to fight future pandemics and protect our International Health Security.