10 Important diseases caused by viruses and fungi in humans

Viruses and fungi are different sets of pathogens that cause diseases.

The diseases caused by them can be obstinate and pose a severe danger to life if the immune system is compromised.

Fevers, jaundice, and colds are common diseases caused by the virus.

While fungi cause systemic (in the blood) and superficial skin infections.

Virus and fungal diseases in humans

These pathogens can cause diseases in both animals and plants.

They are caused mainly by transmission either by physical contact, airborne transmission, or other forms of contamination.

Diseases by the virus in humans

The virus is a non-living intracellular parasite without any metabolic machinery of its own.

These infective agents have essentially nucleic acid as the genetic material enclosed in a protein capsule.

This genetic material can be either DNA or RNA, and some viruses have lipoprotein coats too on the capsid. See the structure of the virus.

They act as parasites for their multiplication by taking over the protein machinery of the host cell.

But once out of the host body, it is difficult for it to survive in the heat and humid conditions and dies.

However, it can infect one person to another and stay inside for long as long as the immune system eradicates it.

They can infect almost all the living cells, i.e., plant cells, animal cells, bacteria, algae, and even yeast cells.

The viral diseases are so devastating that many towns lost a huge population due to viral pandemics. They have spread all over the world by human infections.

Unlike bacteria and other pathogens, these viruses show sudden outbursts leading to many deaths. So they are to be kept under control by the use of vaccines.

List of viral diseases in humans include

1. Skin diseases

Viral diseases like smallpox and chickenpox are skin diseases. There are pustular eruptions on the skin of the infected person.

Smallpox spreads through droplets from the oral or pharyngeal mucosa of the infected person. Chickenpox is spread by direct contact with an infected person.

The symptoms can be severe and, if untreated, can cause death.

Warts are also skin eruptions caused by papillomavirus.

measles virus with glycoprotein tubercles
Measles virus particle with glycoprotein tubercles that help to fix to human cells

2. Gums and buccal cavity: Mumps causes swelling of the throat (parathyroid gland).

3. Brain: Encephalitis, meningitis can cause brain damage and death.

4. Eye: conjunctivitis.

5. Ear: labyrinthitis.

6. Respiratory tract: Flu, Colds, etc.

7. Blood: Measles, AIDS, Dengue fever

8. Bone: Polio.

9. Liver: Hepatitis-B, C, D & E, yellow fever.

10. Heart: Myocarditis.

In plants:

The viruses of plants are quite different from animals. They have different genetic materials. They can cause severe infection to plants in agriculture and farming.

Leaf mosaic: In tobacco, tomato, beans, chili, brinjal, etc.

Malformation of mango, leaf roll, curl in potato and papaya, respectively.

They are treatable using anti-viral drugs to a certain extent.

Diseases caused by fungi

Fungi are multi-cellular microscopic organisms. They can survive as a parasite in the body leading to disease. 

Fungi are spread from external sources to internal. That is, from the skin to blood.

The transmission from humans to humans is very low.

The infection by fungus is mostly two types like

External infection:

  • This is mainly seen on the skin and nails.
  • These are treatable and not so dangerous.
  • They are sometimes influenced by seasonal changes and the food habits of the patient.

1. Skin: They mainly cause ringworm like tenia pedis on foot, athlete’s foot.

It is seen mostly on the skin, nails, foot, hands and groin regions

2. Mucous: Inflammation of mucous membranes like mouth, tongue, uterus, and other body orifices.

3. Ear: causes otomycosis, an infection in the ear by Aspergillus.

4. Eye: Corneal infection called fungal keratitis.

Internal infection. These infections are systematic (i.e., in the blood); they are dangerous and life-threatening.  They can directly produce disease by primary infection. 

Liver: Histoplasmosis is an infection caused by the fungus Histoplasma capsulatum.

Lungs: Cocidiomycosis, which causes pneumonia. It is an infection from external soil to humans by air.

Blood: Candidiasis. It can affect other vital organs like the heart, brain.

Kidney: This type of infection occurs in kidney transplant patients.

But in many cases, the fungal infections are due to secondary infection as a side effect of antibiotic therapy.

In normal conditions, the fungus growth is kept under control by vegetative bacteria.

But when antibiotics are used in disease conditions, the usual friendly bacteria are also killed.

This leads to an uncontrolled invasion of fungi in the body. This is called a secondary infection.

An individual with cancer, diabetes, etc., is also more susceptible to fungal infections.

Ex: Systemic candidiasis, Aspergillosis, Penicilliosis, etc.

Even yeast infections are also prominent nowadays.

Unlike bacteria, fungal cell organelles are not quite different from humans.

So, it is quite hard to target fungi cells without hurting normal human cells.

Thus, using anti-fungal drugs can cause side effects to humans also.

Disease causedFungi responsible
AspergillosisAspergillus fumigatus, A.flavus, A. Niger
BlastomycosisBlastomyces dermatitidis
CandidiasisCandida albicans
CoccidioidomycosisCoccidioides immitis
CryptococcosisCryptococcus neofromans
HistoplasmosisHistoplasma capslatum
MycetomaMadurella mycetomatis
Rhinosporidiosis Rhinosporidium seeberi.
Superficial mycosisTrichophyton, Microsporum, epidemophyton.

Frequently asked questions and answers

What is the most common disease caused by a virus

Flu or cold is the most common disease caused by virus.

How to treat diseases caused by viruses

Virals infections and self limiting diseases which subside on their own in a couple of days. However for chronic diseases one use suitable antiviral drugs if available.

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