What is Pneumonia ?

Pneumonia can be caused by lots of different types of
microbes, and no single one is responsible for as many as
10% of pneumonia cases. For most pneumonia patients,
the microbe causing the infection is never identified.

Additional risk in children include not being breastfeed, exposure to cigarettes or air pollution, malnutrition, and poverty.

The use of acid-suppressing medications – such as proton-pump inhibitors or H2 blockers – is associated with an increased risk of pneumonia.

Vaccines are available for some but not many causes of
pneumonia. The influenza vaccine is effective for those
strains circulating that year, so it should be taken again
every year. The pneumococcal pneumonia vaccines are
recommended for those in higher risk groups (children,
immunocompromised individuals, and seniors).

In the US and the rest of the world, viral pneumonias are
the leading cause of hospitalization of infants. The World
Health Organization has set a high priority on developing
new vaccines and new therapeutic drugs to tackle these
viral pneumonias that largely have no currently available
vaccines or treatments.

Antibiotics can be effective for many of the bacteria
that cause pneumonia. For viral causes of pneumonia,
antibiotics are ineffective and should not be used. There are
few or no treatments for most viral causes of pneumonia.

Antibiotic resistance is growing amongst the bacteria
that cause pneumonia. This often arises from the overuse
and misuse of antibiotics in and out of the hospital. New
and more effective antibiotics are urgently needed.

Being on a ventilator raises especially high risk for
serious pneumonia. Ventilator-associated pneumonia is
more likely to be caused by antibiotic-resistant microbes
and can require the highest antibiotic use in the critically ill
population.

Our changing interactions with the microbial world mean
constantly developing new pneumonia risks. Emerging
infections can lead to epidemics or pandemics, such as from
avian influenza viruses (bird flu), severe acute respiratory
system (SARS) coronavirus, Middle East Respiratory
Syndrome (MERS) virus, and more.

Approximately 10% of people who require mechanical ventilation develop ventilator associated pneumonia, and people with gastric feeding tube have an increased risk of developing of aspiration pneumonia.

Environmental
reservoirs or sources can cause clusters of infection, such as
Legionella pneumonia. Bioweapons can cause pneumonia
such as from anthrax. Vigilance is needed to prevent
pneumonia from becoming an even worse problem than it
already is.

For people with specific variants of FER gene, the risk of death is reduced in sepsis caused by pneumonia. However, for those with TLR6 variants, the risk of getting Legionnaires' disease is increased

While successful pneumonia treatment often leads to full
recovery, it can have longer term consequences. Children
who survive pneumonia have increased risk for chronic
lung diseases. Adults who survive pneumonia may have
worsened exercise ability, cardiovascular disease, cognitive
decline, and quality of life for months or years.

Bacteria are the most-common cause of community-acquired pneumonia (CAP), with Streptococcus pneumoniae isolated in nearly 50% of cases.

. Pneumonia is a huge burden on our healthcare systems.
In the US, pneumonia was one of the top ten most
expensive conditions seen during inpatient hospitalizations.
In 2011, pneumonia had an aggregate cost of nearly $10.6
billion for 1.1 million hospital stays.

The death rate from pneumonia in the US has had little
or no improvement since antibiotics became widespread
more than half a century ago. We are not yet winning the
battle against pneumonia.

Pneumonia does not have effective advocacy. It is not
the subject of fund-raising walks or runs. It does not have
a ribbon or other symbol around which people rally. It does
not get the attention it needs from biomedical scientists or
from research funders. More effort is needed now.

Other commonly-isolated bacteria include Haemophilus influenzae in 20%, Chlamydophila pneumoniae in 13%, and Mycoplasma pneumoniae in 3% of cases; Staphylococcus aureus; Moraxella catarrhalis; Legionella pneumophila; and Gram-negative bacilli

A number of drug-resistant versions of the above infections are becoming more common, including drug-resistant Streptococcus pneumoniae (DRSP) and methicillin-resistant Staphylococcus aureus (MRSA).

The spreading of organisms is facilitated when risk factors are present.

Alcoholism is associated with Streptococcus pneumoniae, anaerobic organisms, and Mycobacterium tuberculosis; smoking facilitates the effects of Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis, and Legionella pneumophila.

Exposure to birds is associated with Chlamydia psittaci; farm animals with Coxiella burnetti; aspiration of stomach contents with anaerobic organisms; and cystic fibrosis with Pseudomonas aeruginosa and Staphylococcus aureus.

Streptococcus pneumoniae is more common in the winter,[18] and it should be suspected in persons aspirating a large amount of anaerobic organisms.

In adults, viruses account for approximately a third and in children for about 15% of pneumonia cases

Commonly-implicated agents include rhinoviruses, coronaviruses, influenza virus, respiratory syncytial virus (RSV), adenovirus, and parainfluenza.