Pneumonia is one of the most common infectious diseases worldwide. In the United States alone, roughly 1.6 million adults are hospitalized for community-acquired pneumonia each year, and globally, pneumonia killed 2.1 million people in 2021. It affects every age group, but its burden falls hardest on young children and older adults.
Pneumonia Rates in U.S. Adults
Among all American adults, the annual rate of hospitalization for community-acquired pneumonia is about 649 per 100,000 people. That translates to nearly 1.6 million adult hospital admissions per year, and this figure only captures cases serious enough to require hospitalization. Many milder cases are treated at home or in outpatient clinics and never show up in hospital data, so the true number of pneumonia episodes is substantially higher.
Age is the single biggest factor driving those numbers up. For adults 65 and older, the hospitalization rate jumps to roughly 2,093 per 100,000, more than three times the rate for all adults combined. That means close to 970,000 older Americans are hospitalized with pneumonia every year. Adults aged 45 to 64 account for another 257,000 annual admissions. The older you are, the more likely a case of pneumonia lands you in the hospital rather than being manageable at home.
Pneumonia in Children Under Five
Pneumonia is the leading infectious killer of young children globally. It accounts for 14% of all deaths in children under five, which amounted to about 740,000 deaths in 2019 according to the World Health Organization. The vast majority of these deaths occur in low- and middle-income countries where access to antibiotics, oxygen therapy, and vaccines is limited.
The causes of childhood pneumonia differ from adult cases. Viruses are responsible for the majority of infections in young children. Respiratory syncytial virus (RSV) is the most common viral cause, while the bacterium that causes the most childhood bacterial pneumonia is Streptococcus pneumoniae. In children with HIV, a specific type of fungal pneumonia can be responsible for at least a quarter of all pneumonia deaths.
Where Pneumonia Hits Hardest Globally
The global burden of pneumonia is not evenly distributed. Sub-Saharan Africa carries the heaviest load, with roughly 500,000 child pneumonia deaths in 2015 alone. South and Southeast Asia follow, with about 200,000 deaths in the same year. Together, those two regions account for more than three-quarters of all pneumonia deaths in children under five worldwide.
Between 2000 and 2015, global hospital admissions for child pneumonia actually increased nearly threefold, with South and Southeast Asia seeing the steepest rise. This doesn’t necessarily mean more children are getting sick. It partly reflects better access to hospitals and better case detection. But it also highlights that pneumonia remains a massive, growing burden on healthcare systems in developing regions.
Viruses vs. Bacteria: What Causes Most Cases
One of the more surprising findings from large U.S. studies is that viruses cause more pneumonia than many people realize. In the CDC-funded EPIC study, which tested hospitalized pneumonia patients for a wide range of pathogens, viruses were detected more often than bacteria in both adults and children.
Among children in that study, 66% of cases involved at least one virus, while only 8% involved bacteria alone. In adults, the breakdown was different but still notable: viruses were found in 23% of cases and bacteria in 11%. A combined viral and bacterial infection showed up in about 3% of adult cases. In more than 60% of adult cases, no specific pathogen could be identified at all, which is a common limitation of current diagnostic testing rather than evidence that the infection wasn’t real.
Hospital-Acquired Pneumonia
Not all pneumonia starts at home. Hospital-acquired pneumonia, meaning infections that develop 48 hours or more after a patient is admitted for something else, occurs at a rate of 5 to 10 per 1,000 hospital admissions. That makes it the most common type of hospital-acquired infection in both Europe and the United States. Patients on ventilators in intensive care units face particularly high risk, since the breathing tube bypasses the body’s normal defenses against airborne germs entering the lungs.
How Vaccination Has Changed the Numbers
Vaccines have dramatically reduced one of the most dangerous forms of pneumonia. Since pneumococcal vaccines became widely available for children in the late 1990s, invasive pneumococcal disease rates in kids under five have dropped by 95% in the United States. For the specific bacterial strains covered by the current childhood vaccine, the decline is even more dramatic: a 99% reduction.
That said, pneumococcal bacteria remain the leading cause of bacterial pneumonia globally, responsible for more deaths than all other bacterial causes combined as of 2016. And antibiotic resistance is a growing concern. More than 40% of pneumococcal bacteria causing invasive disease in the U.S. show resistance to at least one class of antibiotics, which can make treatment more complicated and outcomes worse.
Who Faces the Greatest Risk
The two groups most vulnerable to pneumonia are children under five and adults over 70. Together, these age groups accounted for more than 1.5 million of the 2.1 million global pneumonia deaths in 2021: over 500,000 in young children and more than 1 million in older adults.
Beyond age, several other factors raise your chances of developing pneumonia or having a more severe case. Chronic lung conditions like COPD and asthma make the lungs more susceptible. A weakened immune system, whether from disease, medication, or malnutrition, reduces the body’s ability to fight off the initial infection before it takes hold. Smoking damages the airways’ natural cleaning mechanisms, and recent viral infections like influenza can pave the way for a secondary bacterial pneumonia. Living in crowded conditions or being exposed to indoor air pollution, common in parts of sub-Saharan Africa and South Asia, also increases risk significantly.