A urinary tract infection. A chest infection. A wound that seems small and manageable.
These are among the most common reasons people seek medical care. They’re also where many cases of sepsis begin, often before anyone realises that the body’s response to infection is no longer following a normal course.
Sepsis often develops from infections that initially appear uncomplicated. When the immune system reacts abnormally, it can trigger widespread inflammation that disrupts blood flow, damages organs and, in severe cases, leads to organ failure. Many people don’t recognise sepsis until organ function is already affected.
Across Asia and globally, sepsis remains a major cause of serious illness and death. In many cases, outcomes worsen not because care is unavailable, but because deterioration isn’t recognised promptly. Understanding how sepsis develops and how it presents in everyday life helps explain why timely assessment matters.
What exactly is sepsis?
Sepsis occurs when the body’s immune response to an infection becomes dysregulated. Instead of remaining localised, inflammatory signals spread through the bloodstream, disrupting circulation and oxygen delivery. As this response intensifies, vital organs such as the lungs, kidneys, heart and brain may begin to malfunction. Sepsis can progress rapidly and requires urgent medical assessment and treatment. Sepsis itself isn’t contagious, although the infections that trigger it may be.
When sepsis develops, what’s really happening inside the body explains why an infection that starts off mild can suddenly become life-threatening. According to Prof Ling, Clinical Associate Professor of Department of Anaesthesia and Intensive Care, sepsis is a life-threatening condition where the body’s organs don’t function as a result of an infection.
The disease starts with an infection in the body, which is usually caused by bacteria, viruses, fungi or parasites. As the body tries to fight off the infection, it goes into an overdrive, which causes injury to many important organs in the body.
The key organs and body systems that are affected include the lungs, heart, kidney, brain, liver and blood. When these essential organs and body systems are injured, they can’t function normally and may lead to further injury to other organs and death.
What causes the body to develop sepsis from infection is uncertain. Many factors may contribute to sepsis, including genetics, severity of infection and chronic illnesses.
Where does sepsis usually start?
While sepsis describes the body’s response, it’s almost always triggered by an infection that begins elsewhere.
Common sources include:
pneumonia and chest infections
urinary tract infections
skin and wound infections
abdominal infections involving the bowel and gallbladder
post-surgical or device-related infections
severe viral illnesses such as influenza or COVID-19
Clinicians often describe sepsis according to its source. For example, urosepsis refers to sepsis originating from a urinary tract infection, while pneumonia-related sepsis remains one of the most frequent causes worldwide.
Why sepsis is frequently missed
Early sepsis often resembles common illness. Fever, fatigue, nausea or pain may feel similar to flu or stomach infection, leading many people to expect symptoms to improve with rest or medication. Unlike conditions such as heart attack or stroke, sepsis doesn’t present with a single defining symptom. Instead, it develops through a combination of changes that signal physiological stress. When viewed individually, these changes may appear mild, but when they occur together or worsen rapidly, they warrant medical review. This overlap with routine illness is one of the main reasons sepsis is recognised late.
Because its early signs can resemble the flu or a stomach bug, many people don’t realise they may be developing sepsis. Sepsis itself doesn’t have any classical symptoms, which is why many patients delay seeking medical attention.
Patients usually begin with symptoms localised to the site of infection. These may include cough, sputum or breathlessness in those with pneumonia, or pain during urination or blood in the urine in patients with a urinary tract infection.
When sepsis develops, symptoms may begin to reflect injury to major organs. These include confusion, uncontrolled shivering, passing less urine, severe breathlessness, skin mottling, fainting, and very low blood pressure.
Patients should seek urgent medical care if they experience any of these symptoms.
What is septic shock?
Septic shock is the most severe form of sepsis. It occurs when blood pressure remains dangerously low despite adequate fluid treatment, leading to critically reduced blood flow to vital organs.
People with septic shock often require intensive care support. The risk increases as sepsis progresses.
Once sepsis is diagnosed, treatment focuses on addressing the infection that triggered the condition in the first place. The most important step in reversing organ injury is to treat the underlying infection.
Because antimicrobial therapy and procedures to control infection take time to work, it’s essential to provide life support to maintain vital organ function. This allows patients to survive long enough for the body to overcome the infection.
Modern critical care has a wide range of tools to support failing organs. These include ventilators, medications that raise blood pressure, dialysis machines and heart–lung machines.
Despite decades of research, there’s still no effective medicine, apart from vaccinations, that can prevent or directly treat sepsis itself. For this reason, early treatment of the underlying infection remains essential to control sepsis and allow injured organs to recover.
Sepsis in children and infants
Sepsis can affect people of all ages, including newborns and young children. In infants and children, symptoms may differ from those seen in adults.
Warning signs can include:
- poor feeding or refusal to drink
- rapid breathing or chest indrawing
- unusual sleepiness
- difficulty waking
- fewer wet nappies
- high fever or feeling unusually cold
- pale or bluish skin
- noticeable changes in behaviour or responsiveness.
Because young children can’t clearly describe symptoms, behavioural changes are often the earliest indicator that medical review is required.
Certain groups, including newborns, older adults and people with chronic illnesses, are known to be more vulnerable to sepsis. As Prof Ling explains, because sepsis is an acute condition that affects many of the body’s essential organs, these individuals have less physiological reserve and are therefore more susceptible to severe illness.
Older adults and people with chronic illnesses also tend to have greater difficulty recovering from sepsis due to frailty. As a result, they face a higher risk of recurrent infections and poorer overall outcomes.
Who is at higher risk?
Anyone can develop sepsis, but risk increases among:
newborns and young children
adults aged sixty and above
pregnant or recently post-partum women
people with diabetes, kidney disease or heart disease
individuals receiving chemotherapy or immune-suppressing treatment
However, sepsis can also occur in people with no underlying medical conditions.
What caregivers should watch for
People with sepsis may deteriorate rapidly and may not be able to communicate changes themselves. Caregivers should seek medical review if they notice sudden worsening, new confusion, laboured breathing, cold or blotchy skin, refusal of fluids, or symptoms that worsen after a period of apparent stability.
How to describe symptoms when seeking urgent medical care
Clear communication supports faster clinical assessment, particularly when symptoms are changing quickly.
- what changed suddenly, such as rising fever or new confusion
- how this illness feels different from past infections
- when symptoms began, including approximate timing
- how quickly symptoms progressed
- whether symptoms worsened despite treatment, including antibiotics or fever medication
- difficulty staying awake
- reduced urine output
- persistent shivering
- breathlessness or rapid breathing
- confusion or disorientation
- pain that feels unusual or severe
Always mention any known or recent infection, including urinary, chest, wound, dental, post-surgical or viral illness.
If there is concern, mentioning sepsis as a possibility during assessment can help clinicians understand the urgency of the situation.
Recovery after sepsis is often underestimated
Survival doesn’t always mean full recovery. Many individuals experience ongoing physical, cognitive or psychological effects following sepsis, sometimes referred to as post-sepsis syndrome.
These may include persistent fatigue, muscle weakness, difficulty concentrating, memory changes, anxiety, low mood and sleep disturbance. For some people, recovery extends over months and may require ongoing medical follow-up and rehabilitation.
Since many cases of sepsis begin with common infections such as pneumonia or urinary tract infections, lowering the risk starts with preventing infections in the first place. Prof Ling emphasises that maintaining good everyday personal hygiene is essential in reducing exposure to infectious organisms.
However, one of the most important protective measures is keeping vaccinations up to date. This includes following recommended vaccination schedules for children and receiving the yearly influenza vaccine.
Many readers will relate to the importance of vaccination during the COVID-19 pandemic. COVID-19 is viral sepsis caused by the SARS-CoV-2 virus, and vaccination was a key strategy in reducing the personal risk of developing severe and critical disease.
Personal vaccinations also help protect vulnerable family members, friends and the wider community from infections.
Sepsis often develops from infections encountered in everyday life. The greatest danger lies not in the infection itself, but in delayed recognition when the body’s response becomes disproportionate.
Identifying sepsis depends less on any single symptom and more on recognising change, especially when recovery doesn’t follow the expected course. While sepsis is treatable, outcomes remain closely tied to how early deterioration is recognised and assessed.
Prof Lowell Ling
Clinical Associate Professor
Department of Anaesthesia and Intensive Care
The Chinese University of Hong Kong
X: @LingLing7
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