All about influenza, viruses and pneumonia: Key differences between the three, causes, symptoms

Symptoms of influenza typically include high fever, chills, muscle aches, headaches, sore throat, cough, and fatigue. The onset of symptoms is usually sudden and can be accompanied by a significant drop in energy levels (Image: Canva)

Influenza, commonly known as the flu, is a viral infection caused by influenza viruses. It primarily affects the respiratory system, leading to symptoms such as fever, cough, sore throat, and body aches. Viruses, on the other hand, are microscopic pathogens that require a host cell to replicate. They can cause a wide range of diseases, from the common cold to more severe conditions like HIV/AIDS.

Different from the two, pneumonia is an infection that inflames the air sacs in the lungs, which can become filled with fluid or pus. It can be caused by bacteria, viruses, or fungi, and leads to symptoms like cough, fever, and difficulty breathing.

If you are still confused between these three diseases, here are 7 key differences between the three, according to Dr Hansal Sagar from Delhi.

Definition

Influenza: Influenza, or the flu, is an acute viral infection caused by influenza viruses. It primarily affects the respiratory tract, leading to symptoms such as fever, cough, sore throat, and muscle aches. The disease can range from mild to severe and can sometimes lead to serious complications.

Influenza, viruses and pneumonia:

Virus: A virus is a microscopic infectious agent that requires a living host cell to replicate. Viruses can cause a wide range of diseases, from the common cold and influenza to more serious conditions like HIV/AIDS and hepatitis. They can be specific to certain types of cells or broad-spectrum pathogens.

Pneumonia: Pneumonia is an infection of the lungs where the alveoli (air sacs) become inflamed and filled with fluid or pus. It can be caused by various pathogens including bacteria, viruses, and fungi, and leads to symptoms such as cough, fever, and difficulty breathing.

Causes

Influenza: Influenza is caused specifically by influenza viruses, which are classified into types A, B, and C. Influenza A and B are responsible for seasonal epidemics, while Influenza C typically causes milder respiratory illness.

Virus: The term "virus" encompasses a wide range of pathogens. Examples include rhinoviruses (which cause the common cold), human immunodeficiency virus (HIV), and noroviruses (which cause gastroenteritis). Each virus has its own mode of infection and impact on the body.

Pneumonia: Pneumonia can be caused by various pathogens:

• Bacterial: Commonly caused by Streptococcus pneumoniae or Staphylococcus aureus.
• Viral: Can be caused by influenza virus, respiratory syncytial virus (RSV), or coronaviruses.
• Fungal: Less common, but can be caused by fungi like Aspergillus or Pneumocystis jirovecii.

Influenza: Symptoms of influenza typically include high fever, chills, muscle aches, headaches, sore throat, cough, and fatigue. The onset of symptoms is usually sudden and can be accompanied by a significant drop in energy levels.

Virus: Symptoms vary widely depending on the virus. For example, the common cold often results in a runny or stuffy nose and mild cough, while HIV can lead to flu-like symptoms early on and progresses to more severe immunodeficiency over time.

Pneumonia: Symptoms of pneumonia include a persistent cough (often with mucus), fever, chills, shortness of breath, chest pain, and a general feeling of weakness. Symptoms can range from mild to severe and may vary based on the underlying cause of the pneumonia.

Transmission

Influenza: Influenza spreads through respiratory droplets produced when an infected person coughs or sneezes. It can also be transmitted by touching surfaces contaminated with the virus and then touching the face.

Virus: Transmission methods vary:

• Common cold viruses: Spread through direct contact with infected surfaces or through respiratory droplets.
• HIV: Transmitted through blood, sexual contact, and from mother to child during childbirth or breastfeeding.

• Viral or bacterial pneumonia: Spread through respiratory droplets or close contact with an infected person.
• Fungal pneumonia: Often acquired from inhaling fungal spores from the environment.

Influenza: Diagnosed based on clinical symptoms and confirmed with rapid influenza diagnostic tests (RIDTs) or PCR tests that detect influenza virus RNA.

Virus: Diagnosis involves identifying the specific virus through various methods:

• Blood tests: Can detect antibodies or viral antigens.
• PCR tests: Amplify viral DNA or RNA to confirm infection.
• Viral cultures: Grow the virus from a sample to identify it.

Treatment

Influenza: Treatment includes antiviral medications (e.g., oseltamivir) which can reduce the severity and duration of symptoms. Supportive care such as rest, hydration, and over-the-counter medications for symptom relief is also recommended. Annual vaccination is key for prevention.

Virus: Treatment depends on the virus:

• Some viral infections: Managed with antiviral drugs (e.g., antiviral drugs for HIV).
• Others: Treated with supportive care, as antibiotics are ineffective against viruses.

• Bacterial pneumonia: Treated with antibiotics.
• Viral pneumonia: Managed with antiviral drugs if available and supportive care.
• Fungal pneumonia: Treated with antifungal medications.
• Supportive care: Includes fluids, oxygen therapy, and rest.

Influenza: Complications can include secondary bacterial infections (such as pneumonia), sinusitis, ear infections, and exacerbations of chronic conditions like asthma or chronic obstructive pulmonary disease (COPD).

Virus: Complications depend on the specific virus. For instance:

• HIV: Can progress to AIDS, leading to severe immune system compromise.
• Cold viruses: Can lead to sinus infections or ear infections if not managed properly.

• Respiratory failure: Where the lungs cannot provide enough oxygen.
• Sepsis: A severe body-wide response to infection.
• Lung abscesses: Pockets of pus that form in the lungs.