What Is Pneumonia?

We review your doctor's reference of choice (UpToDate) to understand what Pneumonia is, how it's managed, and its relationship to SARS-CoV-2 pneumonia.

Why Write This?

For about 2 years people have had the term ‘COVID’ on their lips, without necessarily understanding the clinical baggage it carries. When we say that someone has ‘COVID’ what we typically mean is they have SARS-CoV-2 Pneumonia. So, I thought it may be useful for the reader to understand what ‘Pneumonia’ is. It is even more important for people to understand what ‘Community-Acquired Pneumonia’ is and how it relates to SARS-CoV-2 (amongst other causes).

Hold on, what is UpToDate ?

Unless you are a healthcare provider, the likelihood that you have even heard of UpToDate approaches 0% - unless of course, you sell UpToDate. Brief description of the product straight from the horse’s mouth:

UpToDate is a subscription-based online repository of clinical information. “Clinical Decision Support” is a fancy way of saying that doctors go to UpToDate, type in a clinical diagnosis or differential, and figure out what to do next. What did you think they were doing on the computer/phone while you were talking?

Each article is authored by a small group of doctors who have synthesized the available evidence, and hopefully update them regularly.

It is actually a really useful database. Unfortunately, most trainees use UpToDate as a crutch. When being tested on a given medical entity, or looking up information to present on clinical rounds, reciting UpToDate is expected. Rather predictably, this habit persists as students and trainees become licensed doctors. Yet another card in the Tower of Babel that is Centralized Medical Authority - about which I have written previously.

Community-Acquired Pneumonia (CAP)

Pneumonia is an infection of the lung. When discussing pneumonia in a clinical setting, we like to differentiate it based on where it was acquired, because it has a bearing on the likely causative agent, as well as how best to approach managing the infection.

Community-Acquired Pneumonia - refers to an acute infection of the lungs acquired outside of the hospital.

In comparison:

Nosocomial Pneumonia - refers to an acute infection of the lungs acquired in a hospital setting, divided into hospital-acquired pneumonia (HAP) and ventilator-associated pneumonia (VAP).

I’d like to try the following approach in summarizing the UpToDate article on CAP.

Things written in a block will be info direct from UpToDate

Text like this will be my commentary on the information.

Cool? Let’s get started.

What UpToDate knows about Pneumonia

NOTE: When you see CAP, think pneumonia.

Starting with the population-level data…

Epidemiology

CAP is one of the most common and morbid conditions encountered in clinical practice. In the US, CAP accounts for over 4.5 million outpatient and ED visits annually.

CAP is the second most common cause of hospitalization, and the most common cause of infectious death.

Approximately 9% of people hospitalized with CAP will be re-hospitalized due to a new episode of CAP within the same year.

As I’ve tried to explain to friends and family on several occasions, just because there are people admitted to the hospital or in the ICU with pneumonia, does not mean there is a pandemic. Nor does it mean that the causative agent is something we should become hysterical over.

Pneumonia kills. Plain and simple. Thank the Gods we have antibiotics.

Risk Factors

Older age: risk of CAP increases with age. The likelihood of being hospitalized with CAP in adults 65 and older is 3x higher than the general population - which means 2% of the elderly will be hospitalized for CAP annually.

Chronic Co-morbidities - Chronic lung disease, Heart disease, Diabetes Mellitus, malnutrition and compromised immunity.

Viral Respiratory Tract Infection - Viral infections can lead to primary viral pneumonia, but also predispose to secondary bacterial pneumonia. This is most pronounced for influenza virus infection.

Smoking and Alcohol Overuse - Smoking, alcohol overuse ( >80g/day), and opioid use are key modifiable behavioral risk factors for CAP.

Other lifestyle factors - Crowded living conditions, residence in low-income settings, exposure to environmental toxins

As you were reading the above risk factors, you may have noticed how eerily similar they are to those who suffer poor outcomes from COVID-19 pneumonia.

For any doctor worth his salt, this comes as no surprise.

You may have also noticed that viral infections are a risk factor. Viral infections, especially influenza, have a tendency to result in worse bacterial infections - this is called a superinfection. In a prior post, WTF Happened to Influenza in 2020-2021? I summarize an article outlining strong evidence that Influenza infection may be responsible for severe COVID-19 pneumonia.

Common causes of CAP

Streptococcus pneumoniae and respiratory viruses are the most frequently detected pathogen. However, a large proportion (up to 62%) of cases identify no pathogen.

Bacteria: S. pneumonia, H. Influenzae (NOT viral Influenza), S. Aureus, Legionella, Mycoplasma (AKA walking pneumonia - testing looks worse than patient)

Viral: Influenza, Rhinovirus, Parainfluenza, Adenovirus, RSV, Coronaviridae

I would love to type this part out for you, but I feel there’s more impact to read this verbatim from UpToDate:

Read that again, and let it sink in:

1. A pathogen can be identified in only half of the cases of CAP

2. Respiratory viruses have been detected in one-third of cases of CAP, when using molecular testing

One way to think about this is that 50% of cases of CAP have an identifiable pathogen, and approximately 33% of cases of CAP identify a respiratory virus. Back-of-napkin mathematics (33/50 = 0.66) suggests that about 2/3 of pneumonia with an identifiable cause detects a respiratory virus (either alone or with another pathogen) when using molecular testing.

Molecular testing includes modalities like PCR, antigen testing, etc. These are not confirmatory of live virus. Viral cultures are.

Signs & Symptoms

Clinical presentation of CAP varies widely, ranging from mild symptoms like fever, cough, and shortness of breath, to severe signs like sepsis & respiratory distress.

The great majority of patients with CAP present with fever. Other common symptoms include chills, fatigue, malaise, & chest pain.

CAP is also the leading causes of sepsis, with initial presentation which can be characterized by low blood pressure, altered mental status, organ dysfunction (kidney, liver), and platelet/clotting dysfunction.

Again, the overlap here is tremendous. UpToDate also notes that in some patients with severe infection, we can see leukopenia, which is a reduction in white blood cells. Leukopenia was one of the hallmarks we used in the hospital when diagnosing patients to suggest they had COVID-19 pneumonia. Turns out..it’s relatively common in CAP.

Chest X-ray demonstrating opacities in multiple lobes of both lungs, consistent with multi-lobar pneumonia.

Diagnosis

The diagnosis of CAP generally requires demonstration of an infiltrate on chest imaging in a patient with a clinically compatible syndrome (e.g. fever, dyspnea, cough, and sputum production).

For most patients with mild CAP treated as outpatients, microbiologic testing is not needed (apart from testing for SARS-CoV-2). Empiric antibiotic therapy is generally successful, and knowledge of the infecting pathogen does not usually improve outcomes.

Note: Empiric antibiotics means you treat based on suspected setting/cause before you culture the pathogen. You can think of it as similar to prophylactic therapy, based on a gestalt depending on location and other factors.

The above information is critical.

When patients came to the hospital in 2020 complaining of respiratory illness, we would check a few things.

1. Are symptoms bad?

2. Molecular testing

3. Chest X-ray

Even before testing was readily available, we had deluded ourselves into thinking that there were highly specific findings on chest x-rays that could be used to diagnose COVID-19 pneumonia. Unfortunately, what the people were not told, is that by the time the patient got a chest x-ray, they were so far advanced it would be hard to differentiate the findings from other causes of CAP.

Furthermore, the constellation of findings on the X-ray were simply attributed COVID. The problem is, if you let any infection get bad enough, severe inflammation and organ-dysfunction can result in the same type of findings.

Finally, for most patients who would come to medical attention with symptoms of pneumonia, molecular testing is not needed, and treatment is usually successful without knowing the causative pathogen.

The type of viral diagnostic test used vary among institutions. While we generally favor using these tests for patients with severe pneumonia, we interpret results with caution as most multiplex assays have not been approved for use on lower respiratory tract specimens.

In particular, the detection of a single viral pathogen does not confirm the diagnosis of viral pneumonia because viruses can serve as cofactors in the pathogenesis of bacterial CAP or can be harbored asymptomatically.

You saw that right? I didn’t make that up. That was UpToDate. The database of gold standard management algorithms.

• SARS-CoV-2 Pneumonia is a lower respiratory tract infection

  • although the milder Omicron is now being hailed as upper

• Single viral pathogen does not confirm diagnosis

  • and can be harbored asymptomatically

Is SARS-CoV-2 Special?

I will be exploring this question in future posts, but this is an important question in the context of the above.

COVID-19 pneumonia has been heralded as a unique cause of severe CAP. But the problem is that we did not, and are still actively discouraged from treating COVID-19 the same way we treat CAP.

If you go to a clinic or hospital with respiratory complaints, and you do not test positive for COVID-19, you will probably be given Azithromycin, and maybe another antibiotic. If the rapid Flu test comes back positive, they may throw on oseltamivir (Tamiflu) and other helpful drugs - and send you home. You will probably be just fine.

But God forbid your COVID-19 test comes back positive! In that scenario, you get nothing (ok, maybe Tylenol). Recall this point from UpToDate:

For most patients with mild CAP treated as outpatients, microbiologic testing is not needed (apart from testing for SARS-CoV-2). Empiric antibiotic therapy is generally successful, and knowledge of the infecting pathogen does not usually improve outcomes.

Testing is not necessary. Empiric treatment is generally successful. Knowledge of the pathogen does not improve outcomes.

Therefore, they are testing you for COVID-19 to exclude you from the standard treatment paradigm for community acquired pneumonia.

What the hell do you think happens to you then? You go home without treatment. You get worse. Then you come back, severely ill.

Inexplicably, “OMG, look how deadly COVID is!”

To quote Dr. Peter McCullough

“This is wrong.”

Remnant MD ⚡ @RemnantMd

Hearing this for the first time from @P_McCulloughMD at @AAPSonline conference moved me to tears. It was cathartic that someone finally said this. Thank you for your tireless work.

In the next post, we will explore the data and available knowledge on severe pneumonia, to see if COVID-19 pneumonia is indeed as special as we have been led to believe.

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