Common Diseases in Humans: Viral Diseases

During the rainy season, it is common to get sick. Imagine you are travelling in a bus in heavy rain. If someone near you sneezes, there is a high chance for you too to start sneezing in some time. Right? How is it happening? If your friend has a fever, there is a high chance for you to get sick too if you had been in close contact with him or her. 

But a normal headache cannot be spread from one person to another. So there is something that spreads the disease from one person to another. These are disease causing organisms called Pathogens. There are different kinds of pathogens which include bacteria, viruses, helminthes etc. Among these, viral infections are the most common pathogenic disease. Let's discuss more about it.

Table of contents:

• Viral diseases
• Practice problems
• FAQs

Viral Diseases

Viruses aren’t new to us. They are known to cause numerous diseases which can range from mild to deadly diseases. Some of the viral diseases are common cold, hepatitis, COVID-19, flu, mumps, measles, polio, rabies and smallpox. We are going to discuss a few common diseases caused by these viruses. 

Common Cold

One of the most popular and commonly known viral diseases is the common cold. It spreads rapidly and is the most infectious human ailment. The causative organism is Rhinovirus. Transmission can be through cough or sneeze droplets from an infected person or by direct contact with infected surface or person.

Common cold affects the nasal and respiratory tract but not the lungs.

Symptoms of Common Cold

Symptoms usually last for 3-4 days. Symptoms include: Nasal congestion and runny nose, hoarseness in voice, cough, sore throat, headache and fatigue.

Common cold virus cannot be treated with antibiotics.

How to prevent the common cold?

Spread of infection can be prevented by covering the mouth while sneezing and coughing, avoiding crowded areas, wearing a mask and by maintaining hand hygiene.

Flu

Another common viral infectious disease is the flu. People often get confused between the flu and the common cold. Both are viral diseases but caused by different viruses. Flu is caused by Influenza virus. Transmission is through inhaling aerosol from an infected person. 

Flu affects the respiratory system (nose, throat and lungs).

Symptoms of flu

Symptoms of flu are more severe than what is observed in the common cold. These include- coughing with chest discomfort, headache, fatigue muscle ache, fever and chills.

How to prevent the flu?

It can be treated by taking Rest and drinking plenty of fluids. Antiviral drugs are prescribed in case of severe infections.

Common Cold v/s Flu

Polio

You must be aware of polio vaccination camps that occur in your locality in which medical professionals administer oral medicine to children less than 5 years of age. Do you know what this medicine is meant for? Well, oral medicine is a vaccine administered against a viral disease called Polio. It is also known as Poliomyelitis. Years back, it was one of the most dreaded diseases which literally crippled thousands of people for life. Polio is caused by a virus called Polio virus. Transmission of the polio virus occurs through the oral-faecal route.

Oral-faecal route

If a person is defecating by the riverside, faeces will enter the river water and contaminate it. Faecal matter is a rich source of numerous pathogens. This same river water is being used to irrigate crops in the field nearby. Thus, spreading the contamination further to the crops and vegetables. And if we eat those vegetables, we also get infected. This is the oral-faecal route.

Another potential way of transmission is through the flies. Flies usually breed on garbage and rotting material, and faecal matter is no exception. Thus these flies become potential carriers of different pathogens. These flies then sit on food and thus spread the pathogen.

Polio affects the central nervous system, especially the spinal cord and the brainstem.

Symptoms of polio

The symptoms begin with fever, headache, fatigue and nausea.

The symptoms in case of severe polio infections include numbness and tingling feeling in legs, floppy legs and paralysis. No treatments are available for polio infected patients.

How to prevent polio?

Polio infections can be prevented by giving oral vaccines to children. Practising good sanitation and hygiene practices can also prevent polio.

Since the 1960s, polio has been eliminated from most of the world. In 2014, India was officially declared as Polio- free by WHO, thanks to the widespread use of polio vaccines. However, there are countries like Pakistan that are still suffering from Polio every year and the disease is yet to be completely eradicated. 

Rabies

What happens when a person gets bitten by a dog or cat? You must be aware that such affected individuals are suggested to take injections as a preventative measure. Do you know what the injections provide prevention against? These injections are vaccines that help to prevent a deadly disease known as rabies. Rabies is caused by a virus called Lyssavirus.

The transmission of rabies is usually caused by bites and scratches of rabid (suffering from rabies) animals like dogs, cats, rabbits and even monkeys. Rabies also affects other animals. Bites or scratches from such infected animals cause rabies in humans too.

Like the Polio virus, the virus causing rabies also affects the Central nervous system. The most common symptom is hydrophobia or fear of water.

Human-specific viruses

By now you must have understood that viruses not only infect humans but can also infect other animals. But there are some viruses who are picky and cause infection in humans only. Examples of such viruses are those which cause measles, mumps and rubella. 

Measles is caused by Paramyxovirus. The virus causes blisters all over the body. These viruses infect our immune cells.

Mumps is swelling of the parotid glands due to infection caused by Rubeola virus. 

Rubella is caused by Rubella virus which infects lymph nodes. 

Practice Problems of Common Diseases in Humans

1. Match the following:

a. A - III, B - II, C - I
b. A - III, B - I, C - II
c. A - II, B - III, C - I
d. A - I, B - III, C - II

Solution: Rabies is caused by the Lyssavirus.

Measles is caused by Paramyxovirus.

Mumps is caused by Rubeola virus.

Hence the correct option is b.

2. A person is suffering from frequent episodes of nasal discharge, nasal congestion, reddening of eyes and watery eyes. Which of the following diseases is he likely to suffer from?

a. Mumps
b. Hepatitis A
c. Common cold
d. Malaria

Solution: Frequent episodes of nasal discharge, nasal congestion, reddening of eyes and watery eyes are symptoms of common cold which is a highly contagious viral disease usually caused by the Rhinovirus. The virus invades the mucous membranes of the upper respiratory tract, including the nasal cavity, trachea, larynx and pharynx which triggers inflammatory responses in the body. This causes the glands in the mucous membranes to secrete more fluid which is the reason behind the severe nasal congestion and discharge.
Hence the correct option is c.

3. Which of the following body parts is likely to be affected in a person suffering from mumps?

a. Parotid salivary gland
b. Sublingual salivary gland
c. Submandibular salivary gland
d. Thyroid gland

Solution: Mumps is a viral disease caused by a Paramyxovirus which is a member of the Rubulavirus family. The disease causes pain, tenderness, and swelling in one or both parotid salivary glands. 
Hence the correct option is a.

4. Which of the following diseases can be identified by hydrophobia in patients?

a. Flu
b. Rabies
c. Typhoid
d. Polio

Solution: Like the Polio virus, the virus causing rabies also affects the Central nervous system. The most common symptom is hydrophobia or fear of water.
Hence the correct option is b.

FAQs of Common Diseases in Humans

Question 1. What are pathogens?

Answer: Pathogens are those organisms that can transfer the disease causing organism from one person to another. There are different kinds of pathogens which include bacteria, viruses, helminthes etc.

Question 2. What are the symptoms of common cold:

Answer: Symptoms of a common cold usually last for 3-4 days. Symptoms include: Nasal congestion and runny nose, hoarseness in voice, cough, sore throat, headache and fatigue.

Question 3. What do you mean by an oral faecal route?

Answer: If a person is defecating by the riverside, faeces will enter the river water and contaminate it. Faecal matter is a rich source of numerous pathogens. This same river water is being used to irrigate crops in the field nearby. Thus, spreading the contamination further to the crops and vegetables. And if we eat those vegetables, we also get infected. This is the oral-faecal route.

Question 4. How are viral infections caused?

Answer: Viruses are transmitted in many ways. Some can be spread through touch, saliva or through air. Some other viruses are transmitted through sexual contact or by sharing needles that are contaminated. There are some insect vectors like ticks and mosquitoes which can transfer the virus from one host to another.

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