Viral Pneumonia

What is Viral Pneumonia?

Viral pneumonia is a disease caused by a virus that negatively impacts the exchange of oxygen and carbon dioxide in our lungs’ air sacs or alveoli. This usually happens because of inflammation caused by the virus or our own immune response. Traditionally it has been common amongst young children, the elderly, and those exposed to the flu. Before, diagnosing viral pneumonia was tricky, and it was mainly diagnosed by ruling out bacterial pneumonia since the methods for detection (like medical history, physical examination, chest x-rays, and lab tests) weren’t incredibly precise or specific.

The treatments for this type of pneumonia were usually supportive care, which could include giving additional oxygen when necessary, assisting the airway if needed, replenishing fluids, controlling fever and cough, ensuring rest to minimize oxygen requirement, and treating any other existing health conditions or simultaneous bacterial pneumonia.

However, the understanding, incidence, importance, and treatment of viral pneumonia are now undergoing changes for various reasons.

Increasingly more people are at risk of viral pneumonia:

* Society’s longevity and early infant survival rates have created a larger group that’s more prone to viral pneumonia.
* More people are receiving treatments (like radiation or chemotherapy for cancer) that weaken the immune system.
* Hematological/immunological treatments given for chronic illnesses can weaken the immune system.
* The emergence of HIV.
* The increase in illness through antibiotic therapy amongst patients with an inborn immune impairment.
* The increasing number of organ transplants and treatments to suppress the immune system.

There are now better, more precise and quicker tests for viruses:

* PCR (Polymerase chain reaction) is a laboratory technique that copies a group of DNA thousands to millions of times. This technique is being used instead of old methods because the results are obtained much quicker, and it’s not as invasive.
* With the facility of PCR testing, more tests are being performed.
* Many viruses are difficult to grow in the lab and are very sensitive to the sample; PCR overcomes these problems.

Improved testing methods have created a beneficial cycle:

* More test availability has increased the number of diagnosed cases.
* The increase in diagnoses has made medical personnel more suspicious and aware of the disease.
* This heightened awareness has led to more tests being ordered.

There are now safer and more targeted medications for viral pneumonia:

* Before, treatments for viral pneumonia were mainly supportive measures.
* The initial attempts at antiviral therapy were not well received.
* The availability of more specific and effective treatments encourages earlier testing and recognition of the role of viral infections in pneumonia.
* There is now treatment available that can alter the course of HIV.

All these factors, plus the growing role of viral causes in pneumonia and the realization of the role of joint bacterial and viral infections, require a more vigilant approach and early identification of viral lung diseases. To balance this new health load, we now have:

* Better lab detection through ELISA and PCR tests
* Improved radiographic identification with high-resolution CAT scans
* A growing number of safe and effective antiviral drugs
* Enhanced understanding of the role of prevention in viral infectious diseases.

What Causes Viral Pneumonia?

Pneumonia can be a result of different types of infections, particularly in individuals with weaker immune systems. Many different viruses can cause pneumonia, and these can be broadly classified into two categories depending on the type of genetic material they contain – DNA or RNA. However, this classification is not that helpful, so it’s more useful to group these viruses by the kind of illnesses they cause and the people they affect.

There are multiple viruses that are responsible for viral pneumonia:

– Respiratory Syncytial Virus (RSV): It is an RNA virus and is the most common cause of viral pneumonia in young children and babies.

– Rhinovirus: This RNA virus is the most common cause of upper respiratory tract infections across all age groups, but it’s not as likely to cause viral pneumonia.

– Influenza A, B, C viruses: These RNA viruses can lead to pneumonia, with influenza A being the most serious, causing many illnesses and deaths. There are many types of Influenza A, including the bird flu (H5N1) and swine flu (H1N1), which are particularly dangerous.

– Human Metapneumovirus: This RNA virus is increasingly recognised as a cause of viral pneumonia and is believed to have been responsible for the SARS outbreak.

– Parainfluenza viruses type 1, 2, 3, and 4: These RNA viruses are most commonly associated with pneumonia-like illnesses in young children during the spring and fall seasons.

– Human bocavirus and Coronavirus: These RNA viruses can cause pneumonia, mainly in people with weakened immune systems. Some types of coronaviruses can cause the Middle East respiratory syndrome and the severe acute respiratory syndrome.

– Adenovirus: This DNA virus typically causes pneumonia in people who have had organ or blood cell transplants.

– Enteroviruses: These RNA viruses are less commonly associated with viral pneumonia but are frequent causes of poliovirus, gastrointestinal and upper respiratory tract syndromes.

– Varicella-zoster virus: This DNA virus, which causes chickenpox and shingles, can also cause severe types of pneumonia, particularly in people with weakened immune systems.

– Hantavirus: This RNA virus linked to exposure to rodent feces can cause pneumonia, which can lead to rapid respiratory failure and cardiovascular collapse.

– Epstein-Barr virus (EBV): Though this DNA virus is commonly related to mono-like syndromes, it can occasionally cause viral pneumonia in people with blood cell disorders.

– Human herpesvirus 6 and 7: These DNA viruses can potentially lead to pneumonia.

– Herpes simplex virus: Herpes viruses 1 and 2 can cause viral pneumonia in people with weakened immune systems.

– Cytomegalovirus (CMV): This DNA virus is a significant cause of pneumonia in people with a low count of CD4 cells, a type of white blood cell, including those infected with HIV or those who have received organ or blood cell transplants.

– Measles: This RNA virus, though less common in industrialized countries due to vaccination, is still a significant contributor to global child mortality due to viral pneumonia.

– Middle East Respiratory Syndrome (Coronavirus) and Severe Acute Respiratory Syndrome (Metapneumovirus): These are subsets of coronaviruses and can cause serious pneumonia. The Middle East Respiratory Syndrome was first observed in the Middle East and had an initial death rate of 30%.

Risk Factors and Frequency for Viral Pneumonia

There are several clues that can help determine if someone has viral pneumonia. These factors include age, pregnancy, immune competence, and other existing health or societal conditions (comorbid circumstances).

• Age: Viral pneumonia is most common in the very young and elderly. The rate of viral pneumonia decreases from adolescence until middle age, then increases again in later life due to age-related weakening of the immune system.
• Pregnancy: Viral pneumonia can be a risk during pregnancy, especially if it’s related to flu, which is common from late fall to late spring. Major flu epidemics in the past have led to high death rates. This is why the CDC recommends healthy women who are pregnant get a flu shot during their second and third trimesters. Chickenpox can also cause viral pneumonia in pregnant women, and it’s advised they get treatment with a protective medication within 96 hours of exposure if they have not previously been immune.
• Immune competence: A weakened immune system can increase the risk of viral pneumonia. Factors that can weaken the immune system include:
  • Cancer treatments like chemotherapy or radiation
  • Medications to suppress the immune system for treatment of chronic inflammatory illnesses or organ transplants
  • HIV disease that impacts the immune system
  • Inherited conditions that affect the immune system
• Comorbid circumstances: Other factors can also increase the risk of viral pneumonia, including:
  • Trauma
  • Severe burns
  • Uncontrolled diabetes
  • Malnutrition
  • Poverty
  • Environmental exposure
  • Living in group settings

Signs and Symptoms of Viral Pneumonia

Viral pneumonia and bacterial pneumonia can sometimes be hard to tell apart, as there is no specific history or physical signs that give a surefire answer. However, some hints could suggest that the pneumonia is viral rather than bacterial:

• Symptoms come on gradually, not suddenly
• Lower body temperature
• No yellow or green mucus
• History of weakened immune system
• Recent upper respiratory virus, like a cold
• Prior diagnosis of HIV
• History of organ or bone marrow transplant
• History of cancer
• Flu-like symptoms at the same time
• Gastrointestinal symptoms at the same time

In addition, certain signs from a physical examination might point towards viral pneumonia:

• Heartbeat or breathing faster than expected for the body temperature
• Body temperature not as high as you’d expect for how sick the patient is
• Evidence of a corresponding upper respiratory infection
• Skin rash
• Fewer physical signs of lung problems than you’d expect for how sick the patient is
• Signs of infection in both lungs

Testing for Viral Pneumonia

Sometimes, it can be difficult for doctors to determine the cause of pneumonia just by examining a patient’s medical history or conducting a physical examination. The culprit could be either bacterial or viral. Given that we have specific treatments for each type, identifying the right cause is vital. That’s where lab tests, imaging techniques, and a thorough examination can provide crucial insights.

Lab tests are key tools in diagnosing pneumonia. Here are some tests that your doctor might request:

1. Complete Blood Count (CBC) with differential: In simple words, this is a blood test to check the count of different types of cells in your blood. With viral pneumonia, the white blood cell count might be high, low, or even normal. Bacterial pneumonia, however, is often associated with a higher white blood cell count.

2. Chemistry panel: This test helps assess the patient’s hydration level, kidney function, and dosing needs for medications excreted through the kidney.

3. C-reactive protein (CRP): This is a protein that increases in your blood when there’s inflammation in your body. So, it might be high in pneumonia; however, it’s not a guaranteed indication of the disease.

4. ELISA: This is a type of antigen test that detects substances produced by viruses, providing real-time information about the cause of viral pneumonia. It checks for several viruses like Herpes simplex virus (HSV), Respiratory syncytial virus (RSV), Influenza A and B, and Cytomegalovirus (CMV).

5. Gene amplification: This test can detect pneumonia-causing viruses using Polymerase Chain Reaction (PCR) technology. Examples of viruses it checks for include CMV, RSV, HPV, and Coronal viruses.

6. Cytological evaluation: This is a test that studies cells in tissues of the patient. It can provide some insights but can’t diagnose viral pneumonia on its own.

7. Viral culture: It’s the most reliable test to confirm viral pneumonia, but it often cannot be used for urgent medical decisions because the results typically take 10-15 days to come back. The test also has other limitations such as needing a valid specimen and having very specific transportation and laboratory requirements.

Your doctor might also ask for a chest X-ray or a Chest CT scan – although none of them can definitely diagnose viral pneumonia on their own, they can guide the diagnosis by showing signs typically seen in pneumonia.
While tidal infiltrates, lobar consolidation, nodular densities, pleural effusion generally suggest bacterial pneumonia, interstitial infiltrates, patchy distribution of interstitial infiltrates, bilateral infiltrates, or having symptoms of pneumonia but a normal chest x-ray usually indicates viral pneumonia. The advent of thin-section CT scans has greatly improved the diagnosis of viral pneumonia. These scans are particularly useful when symptoms suggest viral pneumonia, but the chest X-ray is normal.

Treatment Options for Viral Pneumonia

Treatment for viral pneumonia centers around a few key points, including supportive care and managing any secondary illnesses.

Supportive care involves multiple steps:
The first is to ensure enough oxygen is delivered to the body. This can mean using a nasal cannula, a noninvasive airway device, or even a mechanical ventilation machine.

Secondly, keeping the body hydrated is crucial. This can be achieved through drinking under supervision or the administration of fluids through a drip.

Thirdly, rest is critical to reduce the body’s oxygen demand and help in the recovery process.

Lastly, the patient’s diet must meet the increased calorie needs due to the additional energy the body uses in its respiratory effort.

Addressing other existing illnesses or conditions the patient may have is also important. The treatment of any underlying bacterial pneumonia that may occur alongside viral pneumonia is one such example.

Studies have shown that bacterial pneumonia often occurs at the same time as viral pneumonia. A notable example is the 1917-1918 influenza pandemic, where most deaths were due to bacterial pneumonia that developed on top of the initial influenza pneumonia.

Specialized antiviral treatments exist for numerous types of viral pneumonia. Additionally, preventative measures are available for those at a high risk of exposure.

For example, influenza can be treated with drugs like oseltamavir, peramivir, or zanamivir. People at high risk can also receive the influenza vaccine or take certain medicines to help prevent the infection.

In the case of Respiratory syncytial virus (RSV), the drug ribavirin can be used. High-risk individuals may also benefit from RSV-specific immunoglobulin or a medicine called palivizumab.

Other viral pneumonias such as those caused by the parainfluenza virus, Herpes simplex virus (HSV), adenovirus, or measles virus, can also be treated with ribavirin. HSV and the varicella-zoster virus (the virus that causes chickenpox and shingles) can be treated with a drug called acyclovir.

However, for some of these viruses, preventative measures may not be available.

In the case of cytomegalovirus (CMV) infection, therapeutics such as ganciclovir or foscarnet can be used. High-risk patients may also benefit from intravenous immunoglobulin.

The varicella-zoster virus can also be prevented by administering the Varicella-zoster immunoglobulin (VZIG).

What else can Viral Pneumonia be?

When a doctor is trying to diagnose viral pneumonia, they have to consider a wide range of other conditions that have similar symptoms. These conditions are:

• Bacterial pneumonia
• Bacterial or viral bronchitis
• Fungal pneumonia
• Lipoid pneumonia, a rare type of lung inflammation
• Sarcoidosis, where lumps, called granulomas, grow in the lungs
• Amyloidosis, a rare disease that causes abnormal proteins in tissues and organs
• Pulmonary edema, a condition caused by excess fluid in the lungs
• Congestive heart failure
• Pulmonary embolism, a blood clot in the lungs
• Pulmonary hypertension, a type of high blood pressure that affects the arteries in the lungs
• Pulmonary fibrosis, a lung disease that occurs when lung tissue becomes damaged and scarred
• Hyperreactive airway disease, a condition where the airways to the lungs are overly sensitive to certain triggers

The doctor uses various tests to check for these conditions, to confirm or rule out viral pneumonia.

What to expect with Viral Pneumonia

The outcome of viral pneumonia varies from case to case, based on several factors. These include:

– The type and severity of the virus causing the infection. For instance, viruses like the Hantavirus, SARS, or MERS generally lead to more serious conditions compared to the RSV or influenza virus.

– The strength of the patient’s immune system. Patients with weakened immune systems, such as those with HIV, typically face a worse prognosis compared to healthy individuals or pregnant women.

– The existence of other health issues in the patient. The presence of conditions such as chronic obstructive pulmonary disease (COPD), heart failure, diabetes, cancer, or abnormal blood conditions can considerably raise the risk and severity of the disease.

– Whether there is a simultaneous bacterial infection.

– The timing of diagnosis and treatment. The sooner the infection is diagnosed and treated, the better the patient’s chance of recovery.

Possible Complications When Diagnosed with Viral Pneumonia

Viral pneumonia can result in various complications such as:

• An additional bacterial infection, which could lead to an abscess, a collection of pus in a body cavity (empyema), or fluid leak between the lung and chest wall (pleural effusion)
• An extreme response to infection known as sepsis, which may lead to multiple organ failure
• Acute respiratory failure, which means severe difficulty in breathing or a decrease in the body’s oxygen content
• Cardiovascular collapse, a sudden loss of blood flow due to heart failure
• Acute respiratory distress syndrome, a severe lung condition causing shortness of breath and rapid breathing

Preventing Viral Pneumonia

Teaching patients about proper care and taking precautions is crucial in dealing with viral pneumonia. Here’s what this involves:

• Patients should be informed about the importance of getting vaccinated against measles and varicella (chickenpox). These vaccinations can protect them from these diseases.
• Patients should also be educated on the importance of getting the flu shot and any treatments needed after exposure to the flu virus.
• Pregnant women should be informed about the flu and chickenpox, especially about the importance of having the vaccinations for these illnesses.
• Preventing HIV and regular check-ups of CD4 cell count (a type of white blood cell that fights infection) are important, along with proper preventive treatment. This is especially necessary for patients with low immunity.
• Special attention should be given to patients with weakened immune systems, including those who are undergoing chemotherapy, radiation therapy, or taking drugs that reduce the body’s ability to fight off diseases. They should be educated on this matter and their health should be closely watched over.