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 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 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.

A 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 is caused by the variola virus, which spreads through droplets from the oral or pharyngeal mucosa of the infected person.

Chickenpox is caused by varicella-zoster virus and spreads by direct contact with an infected person.

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

Warts are also skin eruptions caused by papillomavirus.

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

2. Gums and buccal cavity

Mumps is a contagious disease caused by the mumps virus. It causes swelling of the salivary glands near the throat (parathyroid gland).

The symptoms include headache, fever, loss of appetite, etc.

3. Brain

Encephalitis is an infectious inflammation of brain tissue.

Viruses like West Nile virus, Japanese encephalitis virus, Equine virus, etc can cause it.

Meningitis is another viral infection that causes inflammation of membranes covering the brain and spinal cord.

Enteroviruses, lymphocytic choriomeningitis virus, Influenza virus, and others cause meningitis.

4. Eye

Conjunctivitis is an inflammation of the eye caused by adenovirus, herpes simplex virus, and varicella-zoster virus. It is contagious and spreads from eye secretions.

5. Ear

Labyrinthitis is an ear infection that bacteria and viruses can cause.

Herpes zoster oticus is one of the viruses that cause this ear infection.

6. Respiratory tract:

The influenza virus causes Flu, and the COVID virus causes lung damage.

7. Blood:

Measles is an acute viral respiratory infection.

AIDS is an immunodeficiency disease caused by the HIV virus.

Dengue is a mosquito-borne infection caused by the dengue virus. Here, the platelets deplete dramatically, causing severe risk to life.

8. Bone:

Polio is caused by poliovirus.

9. Liver:

Hepatitis viruses cause liver infection.

Yellow fever is another infection caused by the yellow fever virus.

10. Heart:

Myocarditis is inflammation of the heart muscle wall caused by Coxsackieviruses and adenoviruses predominantly.

In plants:

The viruses of plants are quite different from those of 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 the 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.
  • Seasonal changes and the food habits of the patient sometimes influence them.

1. Skin: Different fungi cause ringworms like tenia pedis infection on the foot athlete’s foot.

Foot with fungal infection (tenia pedia).

This is mostly seen on the skin, nails, feet, hands, and groin regions

2. Mucous:

Inflammation of mucous membranes like mouth, tongue, uterus, vagina, and other body orifices.

Sinusitis is caused by different types of fungi like mucormycosis, Rhizopus, and Aspergillus. Of these, aspergillus species cause fungus balls in pulmonary cavities, leading to sinusitis.

Candida is one of the main fungus that causes vaginal infection.

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: Candidemia is a fungal blood infection caused by Candidiasis. It can affect other vital organs like the heart and brain.

Kidney: Renal candidiasis is a type of infection that occurs in kidney transplant patients.

Details of different species of fungi causing infections are given in the table below.

Sl.NoDisease causedFungi responsible
1AspergillosisAspergillus fumigatus, A.flavus, A. Niger
2BlastomycosisBlastomyces dermatitidis
3CandidiasisCandida albicans
4CoccidioidomycosisCoccidioides immitis
5CryptococcosisCryptococcus neofromans
6HistoplasmosisHistoplasma capslatum
7MycetomaMadurella mycetomatis
8Rhinosporidiosis Rhinosporidium seeberi.
9Superficial mycosisTrichophyton, Microsporum, epidemophyton.

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 in humans.

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 viruses.

How to treat diseases caused by viruses

Viral infections are self-limiting diseases that subside on their own in a couple of days.
However, for chronic diseases, one can use suitable antiviral drugs if available.

Two directly transmitted viral diseases

HIV and Covid are examples of directly transmitted viral diseases.


  1. Biology of Viruses and Viral Diseases
  2. Types of Fungal Diseases
  3. Vaginal Yeast Infection
  4. Viral Meningitis
  5. Fungal Sinusitis
  6. Candidemia (Blood Infection)
  7. What is Polio?

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