Introduction   

The human respiratory system is responsible for breathing which begins with your nose or mouth, down your windpipe (trachea), through bronchial tubes and tiny air sacs called alveoli, to your lungs, and finally into the bloodstream. 

In the bloodstream, oxygen binds to the haemoglobin of the red cells and delivers it to other parts of the body.¹ However, respiratory infections, you to develop illnesses that can interfere with, and have the potential to cause problems with your ability to breathe. Such respiratory infections can be caused by viral infections, such as the human parainfluenza viruses (HPIVs)

Parainfluenza, commonly termed Human Parainfluenza Viruses (HPIVs), are a group of viruses that can cause respiratory infection. These viruses mainly cause harm to the upper and lower respiratory tract. HPIVs may range from mild to severe cases. HPIVs can also affect babies (infants), young children (mostly under the age of five), adults, and the elderly or people who have weak immune systems. It is one of the main leading causes of hospitalization in children less than 5 years old. 

There are four types of HPIVs – HPIV 1-4, each type is associated with certain infectious illnesses like the common cold, croup, bronchiolitis, and pneumonia. These illnesses may range from mild to severe. 

Mild illnesses can go away on their own; severe illnesses may require medical attention as some can be fatal such as cardiac-related illnesses like myocarditis.^2,3 

Myocarditis refers to the inflammation of the heart muscles.⁴ According to the World Health Organisation WHO, viral infections are the leading cause of myocarditis. 

Types of parainfluenza 

Currently, four serotypes of parainfluenza have been identified by the research scientists which include: 

• HPIV1 – it causes harm to the upper respiratory tract and croup
• HPIV2 – it causes cold-like symptoms and croup. It is usually not as common as the other serotypes. It affects children between ages 2 and 5

(HPIV-1 and HPIV-2 approximately make up for about 60%-75% of croup and are found to affect younger children)

• HPIV3 – it mainly causes pneumonia and bronchiolitis in infants in their first year of life
• HPIV4 – it causes respiratory distress and is a less common serotype. It is subdivided into HPIV-4A and HPIV-4B. And can be seen in older children³

Illnesses and complications associated with parainfluenza

If you have caught parainfluenza, you may develop serious health issues as a result. These illnesses may include:

• Croup – swelling and inflammation of the voice box, windpipe, and airways
• Bronchiolitis  
• Pneumonia – inflammation and infection of the lungs
• Common cold 
• Tracheobronchitis – inflammation of the bronchi and trachea

Complications of parainfluenza include:

• Asthma 
• Cardiac complications such as congestive heart failure and rarely, myocarditis
• Chronic obstructive pulmonary disease is inflammation of small air passages in the lungs

A few extremely rare complications of parainfluenza include:

• Encephalitis – inflammation of the brain 
• Meningitis – inflammation of the brain’s lining and spinal cord

Signs and symptoms of parainfluenza

Parainfluenza may present itself in what may look like flu or common cold:

• Fever 
• Cough 
• Stridor
• Sneezing 
• Sore throat, drooling or trouble swallowing 
• Runny nose or nasal congestion
• Redness or swelling of the eyes
• Wheezing 
• Barking cough
• Hoarseness 
• Chest pain
• Decreased appetite 
• Shortness of breath/difficulty breathing   

Risk factors of parainfluenza 

Having a risk factor does not mean that you will get the infection, it simply exposes you to high chances of getting the infection. You are at risk of developing parainfluenza with: 

• Age 
• Weakened immune system 
• Poverty 
• Season (summer, spring, and fall)
• Smoking 
• Vitamin A deficiency 
• Living with infected individuals in close proximity
• People with heart or lung disease 

Diagnosis of parainfluenza

Your physician may take physical examinations of the symptoms you present with and request proper diagnostic tests from the lab. These tests include:

• Swab test; a swab test is usually requested for parainfluenza. It is a test that involves the use of a sterile cotton swab to get the required sample for analysis. Your mucus is the sample that is needed. It is done by inserting the cotton swab at the back of your throat or your nose to collect mucus for clinical examination. It is done to positively identify the type of virus that is causing the illness. The procedure is usually done by a laboratory technician or a nurse and takes a few seconds of your time. It is not painful, but can be uncomfortable; it may make you gag a little bit
• Blood tests; blood tests are used to test if body fluids may show the infection and virus that is causing your symptoms
• Chest X-ray 
• Sputum test; a test that requires you to cough to get mucus from your lungs to be tested
• Bronchoalveolar lavage; a test of the liquid from your lung. It is done by first inserting a narrow, flexible tube, called a bronchoscope, down your throat into your lung. Then a small amount of salt water is injected through the tube to your lungs and finally suctioned out. Your physician or technician will administer a numbing medicine to your mouth and throat^5,6

Management and treatments of parainfluenza 

Specific treatment for parainfluenza is currently unavailable, but there are medications and measures you could take to manage and relieve your symptoms.

Managing your symptoms may include: 

• Taking plenty of rest for fast and proper recovery 
• Consuming lots of fluids to prevent dehydration
• Use a humidifier or take hot showers; these help to increase air moisture in your room, ease breathing, and decrease cough

Medications that may relieve you of some symptoms include:

• Antivirals 
• NSAIDS (nonsteroidal antiinflammatory drugs) – they are drugs that reduce inflammation e.g. aspirin, ibuprofen
• Acetaminophen – these are drugs that reduce minor aches and fever e.g. Tylenol
• Nebulizers in cases of lung congestion
• Inhalers for asthma^6,7

Preventing acquiring or transmitting parainfluenza

Since parainfluenza infections tend to be air-borne, that means they can be transmitted and acquired through air and infected surfaces. You can take the following measures to reduce the spread of the infection (if you are infected) or prevent the chance of getting infected.

If you are infected, you should:

1. Frequently wash your hands with soap and water. If soap and water are not available within your reach, make sure to use hand sanitisers
2. When you sneeze or cough, cover your mouth with tissue or a piece of cloth like a handkerchief
3. Refrain from touching your eyes, nose, or mouth with unsanitized hands
4. Stay at home until your fever and symptoms are gone

Whether you are infected or not, you should:

1. Wear face masks over your mouth and nose to prevent spreading or catching the infection; if you are infected it helps to prevent transmitting the infection to the next person; if you are not, it protects you from catching it in case you come across someone that has it in public. (it is strongly advisable to stay at home if you have the infection)
2. Disinfect surfaces such as your doorknobs, table surfaces, and light switches
3. Avoid sharing personal items such as towels, cutleries, brushes, and sponges⁷

Myocarditis: definition and causes  

Myocarditis is the inflammation of the heart muscle that is commonly accompanied by viruses. Myocarditis can be caused by other factors other than viruses. These factors include:

• Bacterial infections 
• Reaction to toxins
• Autoimmune diseases
• Reaction to certain drugs along with other factors⁴

Parainfluenza and myocarditis

Myocarditis is mostly caused by viral infections. Studies have shown that acute myocarditis is caused, rarely, by the human parainfluenza viruses (HPIVs).⁸ 

It usually occurs when you get the infection, particularly during the infection. When your body senses an infection, your immune system produces antibodies to protect your system from harmful substances; inflammation occurs as a result (immune response). 

During this, you may experience a fever which is a normal response and it shows that your immune system is working hard to fight off those infections. But sometimes viruses in the body are at a high and to combat them, the immune system mistakenly attacks the healthy heart. This causes inflammation in the cardiac muscle and leads to complications.,.

Signs and symptoms of myocarditis

• Chest pain
• Palpitations
• Shortness of breath
• Unusual fatigue 
• Lightheadedness 
• Flu-like symptoms 
• Rarely, swelling in hands, feet, ankles, or legs  

Diagnosis of myocarditis

• Physical assessment  
• History 
• ECG (to record the rhythm, rate and electrical activity of your heart) 
• Echocardiogram (to look at the structure of your heart) 
• Chest X-ray 
• Blood tests 
• MRI (less frequently used)

Management and treatment of myocarditis

Depending on your presented symptoms and cause, precise methods of treatment and management will be crafted to suit you by your consulting physician. A generalized medical treatment may include:

• Painkillers
• Antibiotics (to kill bacteria; if the condition is caused by a bacteria)
• NSAIDS (to reduce or calm inflammation)
• Plenty of rest as needed for better recovery

Summary 

Parainfluenza is a group of viruses that cause respiratory infections that mostly affect infants and young children but can affect the elderly as well as anyone who is infected at all. Parainfluenza can lead to myocarditis, only that, it is rare. Since there are no specific medications available for parainfluenza, it is advisable to take preventative and management remedies to calm or relieve symptoms of parainfluenza and hopefully that could reduce the likelihood of getting viral myocarditis. 

FAQs

Is parainfluenza and influenza (flu) the same? 

No, they are not. However, parainfluenza has flu-like symptoms, making it hard to differentiate by the general public. Flu is common during winter while parainfluenza is common during summer, spring, and fall.

Is there a vaccine for parainfluenza? 

Unfortunately, there is no currently available vaccine for parainfluenza. You cannot be protected from the virus, however, you can always take conscious preventative measures against the virus. 

When should I call my doctor? 

It is encouraged to see your physician when your symptoms do not get better with medications; or when your symptoms worsen.