Infectious diseases and their global impact

Table of Contents

A) Foreword

B) Global impact of infectious diseases
I) Explaining medical and technical terms
II) General information about infectious diseases
1) Pathogenic microorganism
2) Types of infectious diseases
III) Transmission
1) General transmission routes
2) Ebola and HIV
IV) Epidemics example Ebola 2014
1) Outbreak in West Africa: spreading route
2) Triggered by a pathogenic microorganism
3) Methods used for restricting
V) Prevention
1) Immune system preventing infectious diseases
2) Vaccines preventing the outbreak of infectious diseases
3) General tips to reduce the risk of transmission
VI) Treatment
1) Phage therapy
2) Bacteriocins
3) Killing factors

C) Resumé

D) Bibliography

E) Acknowledgment

A) Foreword

Who does not like going on vacation not just in the country you are living, but in extraordinary states? States, only a few have been? Thanks to the invention of air­planes, humans are able to travel around the world, to rarely visited places and to well-known metropolises. More people are moving into the cities, because they are more industrialized than the rural part of the countries and in the cites there is a larger job diversity. These are results of a globalized world and perfect circumstances for a virus to spread. Overcrowded cities, fast travel around the world and mobility. Dr. Larry Brilliant once stated in an interview: “In the last three decades, approximately 30 new diseases have developed with a pandemic character”¹ so “the question is not if one comes, but which virus will it be? When will the outbreak be and how bad will it be?”².

The reason why we are getting ill is the thing that connects us. Outbreaks cannot be avoided but the pandemics and epidemics can be! The disadvantages of being well connected have to be inverse in something positive.

Globalization is not the only push factor for an outbreak of a disease, medicine plays also an important role in this topic. Organ transplantation and antibiotic resistance are necessary to mention, with transplantation the risk of getting infected is higher and without medication that can defeat the pathogenic microorganisms they can spread and become a nosocomial infection, an infection which someone got in the hospital.

Another factor is, that unknown or at least rare diseases and pathogens are brought into industrialized countries from less developed countries LDC or from least developed countries LLDC. Those diseases cannot be treated, because of an insufficient medical care. War and environmental catastrophes are reasons people escape from their mother country into another. There is a large migration flow from LDC and LLDC. These refugees leave everything behind. Everything is left behind in their homeland except their diseases and vulnerable people get infected. With an increasing social inequality, the prevalence (“reflects the number of existing cases of a disease”)³ and incidence (“reflects the number of new cases of disease and can be reported as a risk”)⁴ of infectious diseases are very high.⁵

Diseases spread easily and widely. Infectious diseases are not spatially limited respectively they cannot be in a well connected, industrialized, globalized and engineered world. Everything that is done and will be done, every factor influences our world. Consequently, the question is what global impact do infectious diseases have, how big is the impact and does a small negative factor like infectious diseases predominate all positive factors like fast travel to ulterior region, access to internet in almost the whole world, etc.? This is the topic that will be expounded in this paper.

B) Global impact of infectious diseases

I) Explaining medical and technical terms

Before talking about infectious diseases, their transmission and showing examples, I would like to explain important terms. Also, the text and the sentences are not nested as they would be if explaining everything later. Infectious disease is a difficult subject to understand as it is a medical issue. Therefore, the topics and the thesis are easier to understand.

Infectious diseases are disorders, which can be spread from one living being to another individual and it is caused by pathogenic microorganisms, which are microscopic organism - they cannot be seen with human eyes - that are capable of causing a disease or abnormality. The ability of a microorganism to trigger a disease is called pathogenicity.⁶ In order to survive some pathogenic organisms need a host. A host is usually a larger organism which is infected by a pathogenic microorganism which lives in it. A lot of parasites need an intermediate host, an organism that is infected and in which the parasite develops to an adult, to get to their 'final' host.

If an individual gets infected it becomes contagious. Through i. e. the air, when the contaminated coughs, millions of the bacteria get in the air and can infect other humans. When it is just a spatially and temporally limited outbreak of a disease it is called an epidemic. An example would be the Ebola epidemic not only in 2014 but also in 1976 or the common dangerous weight problem: adiposity. More dangerous than an epidemic is a pandemic when the outbreak of a disease is just temporally limited but not spatially and worldwide like the acquired immune deficiency syndrome (AIDS). Nevertheless, an occurrence of a disease in spatially limited but temporally prolonged fashion is more devastating. It is called endemic and an example would be smallpox or malaria.

II) General information about infectious diseases

1) Pathogenic microorganism

Pathogenic microorganisms are causing a disease to their host and are capable of carrying on the living process. Bacteria, fungi, virus, and protozoa are types of pathogenic microorganisms and they are causing the disease by multiplying with­in their host. In the following, the different organisms are being explained more specifically.

Let's start with the Protozoa, it is a single-cell organism with many simi­larities to higher and more complex individuals and organisms. In order to multiply they use the asexual and sexual mode of propagation. In contrast to many other pathogenic microorganisms, the protozoa cannot survive without a host!

Fungi are other parasites, they are numbered among to the Eucaryotic cells with a 'real' nucleus. Fungi look much like a plant cell without chromatophores. Like protozoa, they propagate asexual and sexual.

Bacteria have no 'real' nucleus and as a result, they belong to the procaryotic cells. It consists mostly of a DNA-Ring, cytoplasm, ribosomes, cell wall, capsule, and a plasma membrane. Even though it has so many components it is the second smallest unit and it appears in the shape of rods and spheres. This organism does not need a host to survive, like the aforementioned pathogenic microorganism. Although bacteria can survive on its own some depend on oxygen and for other types of bacteria it is life-threatening and even poisonous. These procaryotic cells propagate asexual and do not need a sexual partner as it conducts mitosis.

The smallest unit with a secured cell structure and a pathogenic micro­organism is the virus. It is able to survive without a host - in contrast to protozoa and fungi - but without a host, a virus cannot propagate, which is purely intracellular. There are at least two chemical constituents of which it consists: Proteins and either DNA or RNA. Peter Medawar cut right to the chase of the matter by saying: "A virus is a piece of bad news wrapped in protein."⁷

2) Types of infectious diseases

There are two different types of infectious disease respectively two different types of infections, the primary and secondary infection. A primary infection occurs when an organism first meets a pathogen, it is called the first infection as there are no innate defenses (antibodies) against the pathogen. Four types of infections make for primary infection. Ebola and HIV (Human Immunodeficiency Virus) are examples for the viral infection, which appears when a virus invades a host and attaches themselves to a cell. As they enter the cell the pathogen releases its genetic material that allows the virus multiplying.

Fungal infection - the second type of primary infection - can decompose and absorb organic matter using enzymes and once they have entered the body it is difficult to eliminate the pathogen. A parasite infection is also characteristic for primary infections, it enters a host and drains the energy, the host dies and the parasite has to look for the next victim. A bacterial infection is the last kind of infection which can trigger a primary infection though it tends to the secondary infection as it usually enters the body after the host is weakened by a virus.

A secondary infection is not an infection occurring when an organism gets infected the second time by the same pathogenic microorganism but rather it occurs if the body is already weakened by a pathogenic microorganism and in addition, another pathogen infects the human body. So, the organism is infected with two different infections at the same time.

Infectious diseases can also be sorted by transfer destination. There are anthroponotic diseases and zoonotic diseases. Anthroponotic diseases are disorders caused by human pathogens, which only evoke symptoms in a human body.

Animals can contain the pathogen within oneself and can transmit it to human without becoming ill. Diseases which can occur in vertebrates and humans are called zoonotic disorders. They can be split into two different subgroups, the anthropozoonosis, which describes the transmission of a sickness from human to animal and if the disorder is transmitted from the animal to the human body it is called zooanthroponosis.

III) Transmission

1) General transmission routes

Diseases are being transmitted directly and indirectly. If there is a physical contact between an infected and susceptible person, the transmission occurs directly. As a result, an indirect transmission ensued when there is no human-to-human contact and the transmission happens from a reservoir to contaminated surfaces or from a reservoir to vectors such as mosquitoes, flies, ticks or rodents.

Infectious diseases can be transmitted through different routes. Meningitis or tuberculosis are transmitted through air droplet i. e. through inhalation or eye contact with contaminated droplets as a result of close interaction with an infected person. When ingesting fecal matter pathogens for diseases like cholera, salmonella or Hepatitis A may enter your body, this route is called Faecal-oral. Having unprotected sex can lead to HIV, syphilis or Hepatitis B, but also during childbirth or when breastfeeding a mother can pass these diseases to her child.

The Vector-borne transmission route takes place through a mosquito, sand fly bites and bites of lice and ticks. Malaria and dengue fever are passed by the vector-borne route. Tetanus develops thru deep cuts with an unclean object or an infection of the umbilical cord after birth. HIV and Hepatitis B and C are transmitted through the blood by using unsafe injections or a transfusion with unsafe blood.

2) Ebola and HIV

In the 21st century 75 % of all infectious diseases are zooanthroponosis, disorders transmitted from animals to humans. Ebola and HIV are infectious diseases which were transmitted from animals to humans, thus zooanthroponotic diseases.

Let's start with general information about Ebola. The Ebola virus disease (EVD) is a rare and deadly disease, most commonly affecting humans and non­human primates like monkeys and gorillas. It is caused by the Zaire Ebola virus. It is believed that the virus origin is in fruit bats, they do not die of EVD as they are the host for the virus. Through contact with other animals or humans, the virus found its way into the humans' world. Regardless of whether the transmission occurs between animals or from animal to humans, the transmission ways are the same, but as we take a closer look on humans, the ways are being explained relating to humans.

Through direct contact with blood or body fluids like urine, semen, breast milk or feces of a sick person or a person who died of EVD respectively of the hemorrhagic fever and its consequences (a closer look at IV, 2 Triggered by a pathogenic microorganism). Other ways to transmit the Zaire Ebola virus disease are through direct contact with objects like needles contaminated with infected body fluids, through direct contact with infected food like bush meat or fruits and with contact of infected fruit bats or nonhuman primates.

HIV, Human Immunodeficiency Virus, triggers the disease AIDS (Acquired Immune Deficiency Syndrome), a disease with many symptoms and only when considering them in general and all, AIDS is the disorders name. 37 million people contract HIV in 2017⁸. The virus origin is in chimpanzees and was transmitted to humans, as a result, the disease AIDS is affecting both, humans and chimpanzees. The Human Immunodeficiency Virus weakens the immune system and as a consequence, the immune defense is not working efficiently. People are actually not dying from this disease, but they are dying from other infections, their body could not defeat. The transmission of the virus is similar to the transmission of the Zaire Ebola virus. It is important to know, that not the disease is being transmitted and not the disease is actually spreading, but in the first place, it is the pathogen. Anyway, like the Ebola virus, HIV can be transmitted through body fluids like blood, also during childbirth and breastfeeding and unprotected sex.

IV) Epidemics example Ebola 2014

1) Outbreak in West Africa: spreading route

The Ebola outbreak in 2014 which turned into an epidemic, was not the first one. It all started in 1976 in Zaire, which is now known as the Democratic Republic of Kongo. Mabalo Lokela was the first victim of the Zaire Ebola virus and he probably has eaten monkey meat when he traveled through the northern part of the country.

After getting fever he went to the hospital, where he was diagnosed with malaria, as they have the same symptoms, many people were sick with malaria and nobody knew about the Zaire Ebola virus. In this time and this region, the hospitals were in a financial crisis, so they shared the same injection needles with a lot of patients. The virus had the perfect circumstances and could spread. This first outbreak had a mortality rate of 88% and 280 victims.⁹

Until 2010 there were just two laboratories in Germany, which had the permission to work with the virus and a Biosafety Level of 4 (BSL 4). One year later, in 2011 the Ebola virus and hemorrhagic fever were sketchily explored. Today living in 2018, the virus and the fever are better known, yet it is just possible to treat the symptoms and hope that will be enough. There are vaccinations but hardly any are authorized.

The outbreak in 2014 was the biggest and the worst Ebola epidemic since the outbreak in 1976. It all started in Guinea in December 2013, when a two-year- old boy played in the woods and got presumably in contact with feces of the infected animal or with the animal itself. The animal was probably a bat.

[...]

¹ The Unseen Enemy, dir. Janet Tobias, CNN Films, Sierra/Tango and Vulcan Productions, 2017.

² Dr. Brillian in The Unseen Enemy, dir. Tobias.

³ M Noordzij, FW Dekker, C Zoccali, KJ Jager, “Measures of disease frequency: prevalence and incidence”, 19 February 2010 <https://www.ncbi.nlm.nih.gov/pubmed/20173345>.

⁴ M Noordzij, FW Dekker, C Zoccali, KJ Jager.

⁵ Cf. Alexander Krämer and Ralf Reintjes, Infektionsepidemiologie: Methoden, Surveillance, Mathemathische Modelle, Global Public Health, (Berlin: Springer, 2003) 11-12.

⁶ Cf. John Yarnell, Epidemiology and prevention: a system-based approach, (Oxford: Oxford University Press, 2007) 182.

⁷ Stefan Kaufmann, The new Plagues: Pandemics and Poverty in a Globalized World (London: Haus Publishing, 2009) 9.

⁸ Unseen enemy. dir. Janet Tobias. CNN Films, Sierra/Tango and Vulcan Productions, 2017.

⁹ Cf. Matthias Neufeld, “Die Geschichte des Ebolavirus 2011, Biologische Killer: Epidemien und Pandemien, eds. Sarah Bottaccio, Lena Köblin, et all (Norderstedt: Science Factory, 2014) 75­90, at 80.