Differentiating Between Causes of a Disease and Risk Factors 

What are the Causes of a Disease & Risk Factors of a Disease?

A lot of the audience is confused about what are the causes of a disease and what are the risk factors of disease? To assess the causes of a disease and risk factors associated with disease phenotypes, it is obligatory to see through what are, these causes and risk factors in medical sciences. So, in epidemiology, a health-modifying agent is known as Cause. While risk factors are factors that increase a person’s chance of developing a disease. In this post we aim to pay attention to the causes of a disease and in addition, to discuss the risk factors of a disease. Please see detail information about the human abnormalities due to abnormal cells,”The Mystery Behind Several Disorders of Human are Different Types of Abnormal Cells”

Principally our target of discussion will be confined to infectious diseases. There are a group of diseases caused by microbes known as pathogenic microorganisms. These microorganisms are usually viruses, bacteria, fungi, parasites, etc. (WHO EMRO, n.d.). Almost all infectious diseases have some causing agents in the form of pathogenic organisms (such as viruses, bacteria, fungi, protozoa, helminths, etc.).

Causes of a Disease: Viral Invasion and Body Immune Response

Unquestionably, viruses belong to different groups. They invade the human body and use host body genomic DNA replicating machinery for its reproduction. Moreover, viral particles invade host body cells and pass through different stages (incubation, prodromal, illness, decline, convalescence) (Eske, 2021) to develop unhealthy phenotypes in the infected individual. In the meantime, the host’s immune system begins to fight against foreign antigens to remove them from the body. The host immune responses to the invaded viral particles come in different forms (i.e., cell-mediated immunity (e.g., T lymphocytes), Antibody, NK cells, and macrophages, lymphokines and monokines, etc.) (Klimpel, 1996). However, a weak immune system of the body facilitates invaded microbes to produce disease phenotype. For the same reason, table 01: shows some common viral diseases and their causing agents. 

Causes of a COVID-19 Disease: The Recent Pandemic

Obviously, as organized in the table below, recently we have seen COVID-19 Pandemic across the world.  Furthermore, according to the reported studies, severe acute respiratory syndrome coronavirus 2, (abbreviated as SARS-CoV-2) is the main cause of this disease. This virus infected a lot of humans, but some got disease, and some remained healthy. Undeniably, all those infected by this virus have some risk factors mentioned in the table. So, these risk factors play a leading role in disease morphology. In conclusion, according to the UNO COVID-19 Dashboard, this virus has infected approximately 768 million people belonging to almost all territories of the world. Despite COVID-19-infected, nearly 7 million have given up their lives. In contrast, the estimated death rate is approximately 1 in 110 in infected people (WHO coronavirus (COVID-19) dashboard, n.d.). 

Table 01: Virus Mediated Some Common Human Diseases
Viral Disease	Causing Agents	References
COVID-19	SARS-CoV-2.	(Admin, 2018),
Common cold	Rhinovirus, coronavirus, and adenovirus
acquired immunodeficiency syndrome (AIDS)	human immunodeficiency virus (HIV)
Hepatitis	Hepatitis A/B/C viruses,
Smallpox	Variola virus
Herpes Zoster	varicella-zoster virus (common name chickenpox)
Influenza	Influenza virus (RNA virus)
Measles	Rubeola virus
Mumps	Paramyxovirus
Poliomyelitis	Poliovirus
Encephalitis	Herpes Simplex Virus
Rabies	Rabies lyssavirus

Causes of Microbial Infection-associated Human Disease

Although this may be true that approximately one trillion microbes exist on Earth. However, a very less number, about one in a billion, is considered human pathogen with a total figure of 1400 that is described as human pathogens (Microbiology by Numbers, 2011). Besides, human pathogens, bacteria are not always harmful to us. Most bacteria play essential roles i.e., vital to the health of living organisms. Therefore bacteria, having a beneficiary role, and described as “Good Bacteria”. However, few of them act like pathogens and compromise living organisms’ health. Therefore, these health-risk bacteria are known as “Pathogenic bacteria” (Balloux and van Dorp, 2017) that involve in causing roughly 26 human infection diseases.

These pathogenic bacteria can enter/transfer to humans either through zoonotic contact or through waterborne sources (Vouga and Greub, 2016). Then causes number of infectious diseases including Pneumonia, tetanus, typhoid, and tuberculosis (TB). Evidently in Table 02, some bacterial diseases along with their causing agents are tabulated. 

Table 02: Some Common Bacterial Diseases and Their Causing Agents
Bacteria Disease	Causing Agents	References
Pneumonia	Streptococcus pneumoniae	(Common bacterial diseases, 2022),  (Vedantu, n.d., Reportable Invasive Bacterial Diseases, n.d.,)
Urinary tract infections (UTI)	Escherichia coli
Meningitis	Neisseria meningitidis
Tetanus	Clostridium tetani
Syphilis	Treponema pallidum
Pseudomonas	Pesudomonas aeruginosa
Plague	Yersinia pestis
Gonorrhoea	Neisseria gonorrhoeae
Botulism	Clostridium botulinum
Salmonesllosis	Salonella enteritis

Causes of Tuberculosis Disease

Tuberculosis (also known as TB) is an infectious disease. After all, Mycobacterium tuberculosis is the cause of morbidity and mortality in TB patients. Finally, TB is the 3rd leading cause of death (after COVID-19 and HIV) among infectious diseases. Please read in detail (Huang et al, 2022). Risk factors (given in Table) further enhance the chance of TB in the case of Mycobacterium tuberculosis infection. 

Athlete’s Foot: An Example of Causes of a Mycosis (fungal infection) Disease

On the other hand, Athlete’s Foot is caused by Trichophyton rubrum, a dermatophytic fungus, and risk factors, which can enhance the chance of mycosis, are given in the table. Similarly, fungal infections are the causes of many diseases as described in Table 03.

Table 03: Fungal Diseases and their Causing Agents
Fungal Diseases	Causing Species	References
Candidiasis	Candida albicans, C. glabrata, C. parapsilosisC. tropicalis	(Fungal Disease-Specific Research, n.d.)
Cryptococcosis	Cryptococcus neoformansC. gattii
Aspergillosis	Aspergillus spp.
Blastomycosis	Blastomyces dermatitidis
Coccidioidomycosis (Valley Fever)	Coccidioides immitisC. posadasii
Histoplasmosis	Histoplasma capsulatum
Pneumocystis pneumonia	Pneumocystis jirovecii

Protozoa: The Major Causes of a Protozoal Disease

Surprisingly, protozoa are likely other microbes’ unicellular organisms. But unlike other microbes they are eukaryotic, having complex internal structure and metabolic activities. Protozoal Diseases are also one of the major classes of human infectious diseases. Here we take the case of some well-known examples of protozoal diseases and their causing agents (table 04). 

Table 04: Protozoal diseases and their causing agents
Protozoal Disease	Causing Agent of Protozoal Diseases	Reference
Amoebiasis	Entamoeba histolytica	(Admin, 2022), (Andrews et al, 2014)
African sleeping sickness	Trypanosoma brucei gambiense
Cryptosporidiosis	Crytoptosporidium parvum Cryptosporidium hominis
Diarrhoea	Giardia lamblia
Inflammation of urogenital tract	Trichomonas vaginalis
Leishmaniasis	Leishmania spp.
Toxoplasmosis	Toxoplasma gondii
Malaria	Plasmodium spp.
Visceral disease	Leishmania
Watery diarrhoea	Cryptosporidium

Helminths-mediated Human Diseases

On the whole, helminths describe parasitic worms. In fact, these worms are of two types, such as Playthelminthes and Nematoda. Thus, morphologically playtheminthes are flatworms and the other one is roundworms. Furthermore, these worms are the most common infection causing agents in humans (Hotez et al, 2008).

Table 05: Helminths-mediated disease and their causing agents
Helminth-mediated Disease	Causing Agent	Reference
ascariasis	Ascaris or roundworm (Ascaris pneumonitis)	(Helminth infections: diagnosis and treatment, 2015), (Hotez et al, 2008)
cysticercosis	Taenia solium or pork tapeworm
enterobiasis	Enterobius vermicularis or pinworm/threadworm
schistosomiasis (bilharziasis)	Schistosoma mansoni
taeniasis	Taenia saginata or beef tapeworm
Trichururiasis	Trichuris trichiuria or whipworm,
Echinococcosis (Hydatid disease)	Echinococcus granulosus Echinococcus multilocularis
Filariasis	filariae nematode
Onchocerciasis	Onchocerca volvulus
Loiasis (African eye worm),	Loa loa

Risk Factors of a Disease

In brief, risk factors can only enhance the chance of disease, irrespective of initiating disease. So, disease-causing agents trigger disease in the body. Therefore, the severity of the disease depends upon the presence of risk factors. For instance (table 06). For example, recently we have gone through the COVID-19 pandemic due to the infection of SARS-CoV-2 virus, a causative agent of COVID-19. Different tests show that SARS-CoV-2 infected millions of people but many of them didn’t show signs and symptoms of the COVID-19 disease. However, many people developed severe COVID-19 conditions. In addition, Scientific data on COVID-19 patients show that its severity has strong correlation with diabetic and lung-cardiac problems (Puri et al., 2021).   

Table 06: Examples of Causes of Infectious Diseases and Risk Factors
Disease	Disease Causing Agent (e.g)	Nature of Causing Agent	Risk Factors (chance increasing factors)	References
COVID-19	severe acute respiratory syndrome coronavirus 2, (SARS-CoV-2)	Virus	Age (old) and Gender (male), Heart and lung diseases, Hypertension,  Overexpression of (ACE2, TMPRSS2, and   , Pro-inflammatory cytokines, etc.)	(Zhang et al, 2023)
TB	Mycobacterium tuberculosis	Bacteria	Personal (age/gender, immune system, alcohol, malnutrition, smoking)Social Contact (crowding, direct contact TB infected person, health occupational risk,  improper ventilation, family history) Already patient of the following diseases (Diabetes, HIV infection, Bacillus Calmette–Guérin (BCG) scar)	(Narasimhan et al, 2013)(Kirenga et al, 2015)
Athlete’s foot	Trichophyton rubrum	Fungi	Personality base (age and gender)Activity based (physical activities , occupation)	(Perea et al, 2000)
Malaria	Plasmodium species (P. malariae, P.falciparum, P.vivax, P.ovale, and P.knowlesi)	Protozoa	Personality (age and gender, living in malaria infected area, types of residence (more chance in open house without net, worse hygenic condition)	(Talapko et al, 2019), (Nyasa et al, 2021)
	Helminths

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