When the human body encounters harmful pathogens like bacteria, viruses, fungi or parasites, the immune system kicks into action to fight off the infection and prevent it from spreading and causing damage. An infection occurs when these infectious agents invade the tissues and multiply there, leading to tissue injury and disease. Mild infections may cause no symptoms or only local inflammation and discomfort. But severe, widespread infections can have serious consequences if left unchecked. So what actually happens inside the body when it is overwhelmed by infection?
How Infection Spreads in the Body
Infectious pathogens usually enter the body through the skin, mouth, nose or urogenital openings. For example, a bacteria on your hands can enter through a cut in your skin, or a virus in the air can be inhaled and get lodged in the lungs. Once inside, these invaders use clever tricks to avoid detection and multiply rapidly.
Viruses need to get inside host cells and hijack the cell’s machinery to make more copies of themselves. Bacteria release toxins that damage tissues and help them invade deeper. Fungi and parasites secrete enzymes to digest tissues for their nutrition. They use surface proteins to adhere to cells and evade the immune system.
As the infection grows, the pathogens spread from the initial site of infection into the bloodstream and lymphatic system to reach all parts of the body. This spreading of infection to distant sites is called dissemination. The bloodstream helps rapidly distribute the germs throughout the body, while the lymphatic system also carries them to lymph nodes where they can grow unchecked.
The Immune Response to Infection
The immune system has an array of cells and proteins that work together to continuously monitor the body for signs of infection. Its job is to identify foreign invaders, contain them and eliminate them before they can cause harm.
Innate immune response
The inborn or innate immune system forms the first line of defense against infection. It responds within hours of recognizing pathogen associated molecular patterns or PAMPs on bacteria, viruses etc. using pattern recognition receptors or PRRs.
Phagocytes like neutrophils and macrophages are innate immune cells that engulf and destroy pathogens. Other immune cells like natural killer cells (NK cells) kill virus-infected cells to stop viral replication. Proteins called complement assist in microbial killing.
Chemical signals like histamine and cytokines released by innate immune cells lead to inflammation at the site of infection. This helps block spread of infection but also causes redness, swelling, heat, and pain.
Adaptive immune response
If the innate response is unable to eliminate the pathogen, the slower but more specialized adaptive or acquired immune response kicks in. It involves T lymphocytes and B lymphocytes or T cells and B cells.
T cells directly kill infected cells and enhance the phagocytic activity of macrophages. B cells produce antibodies that mark pathogens for destruction and prevent their growth. The adaptive response also creates immunological memory so any subsequent encounter with the same pathogen leads to a stronger and faster response.
Systemic Effects of Severe Uncontrolled Infection
When the immune system is overwhelmed by a widespread invasive infection, it can have detrimental effects on many organ systems and homeostasis in the body.
Fever
One of the most common effects is a fever or high body temperature. The hypothalamus in the brain responds to pyrogens or fever-producing substances released by immune cells by raising the body temperature set point. This creates an overall inflammatory state in which higher body heat inhibits pathogen growth.
Shock
Septicemia or blood poisoning can lead to septic shock – a dangerous drop in blood pressure that prevents organs from getting adequate oxygen and nutrients. Toxins released by bacteria reduce vasoconstriction and cause blood vessel dilatation, reducing blood supply to organs and precipitating shock.
Difficulty breathing
Lung infections like pneumonia can impair oxygen exchange and carbon dioxide elimination in the lungs. Fluid buildup, pus and inflammation in the alveoli or air sacs hampers gas diffusion. This can cause respiratory distress, shortness of breath, cough, hypoxemia and respiratory failure.
Dehydration
Vomiting, diarrhea, sweating from fever and poor intake all contribute to loss of fluids and electrolytes like sodium, potassium and chloride from the body. Dehydration can disrupt cell functioning and organ perfusion.
Heart damage
Certain pathogens like viruses that cause myocarditis or bacteria that release toxins into the bloodstream can directly damage and weaken the heart muscle, leading to arrhythmias, heart failure or even heart attack.
Kidney dysfunction
Toxins and inflammation can cause acute kidney injury and reduce urine output. Waste builds up in the blood leading to imbalances in electrolytes, fluids and salts. Dialysis may be needed to filter the blood.
Liver dysfunction
The liver helps filter toxins and bacteria from the blood. Infections impair its ability to metabolize nutrients, produce proteins, eliminate bilirubin and regulate blood clotting factors. This can manifest as jaundice, easy bruising/bleeding, changes in mental status, etc.
Altered mental status
Fever, dehydration and sepsis combined with impaired organ function can lead to confusion, drowsiness, seizures or even coma. Sepsis-associated encephalopathy causes altered brain signaling. Meningitis infections directly affect the brain.
When to Seek Emergency Care
While mild infections can be managed with rest, fluids and over-the-counter medications, severe disseminated infections are medical emergencies requiring prompt care. Emergency warning signs include:
- Difficulty breathing, rapid breathing, shortness of breath
- Blue color to lips or nails
- Altered mental state like disorientation, unresponsiveness or confusion
- Chest pain
- Severe dehydration – dry mouth, little or no urination, sunken eyes
- Fever above 103 F (39.4 C)
- Drop in blood pressure indicated by dizziness upon standing
- Seizures
- Uncontrolled bleeding or easy bruising
If someone has a suspected severe infection along with any of these symptoms, call emergency services or take them to the nearest emergency room right away. Waiting it out to see if they improve on their own can have grave consequences.
Diagnosing Widespread Infection
Doctors use a combination of approaches to diagnose and identify the source of infection:
Patient History
Information like symptoms, when they started and any sick contacts helps gauge infection likelihood. Recent surgeries, medical devices or health conditions that compromise immunity also raise suspicion for infection.
Physical Examination
Checking temperature, pulse, blood pressure and respiratory rate helps assess overall status. Listening to lungs and heart, pressing on abdomen to check for pain, rashes, swelling or discharges at surgical sites or IV lines provide vital clues.
Blood Tests
Complete blood count, cultures, CRP levels and erythrocyte sedimentation rate help confirm infection and inflammation. Metabolic panels identify organ dysfunction. Procalcitonin is a marker more specific to bacterial infections compared to viral ones.
Imaging
Chest x-rays, ultrasounds, CT scans and MRIs visualize internal organs and tissues to pinpoint pockets of infection like pneumonia or abscesses that require drainage.
Microbiological cultures
Samples of blood, sputum, fluids or pus from infection sites are analyzed to identify the type of pathogen growing and its antibiotic sensitivity profile. This confirms the diagnosis and directs treatment.
Treating Disseminated Infections
Along with addressing underlying health issues, treatment focuses on clearing the infection and supporting vital functions:
Antibiotics
Once lab tests confirm the pathogen and its susceptibilities, appropriate antibiotics are started intravenously. Fast acting broad spectrum antibiotics are given first, then narrowed once cultures specify which ones the infection responds to. The full course is completed to prevent resistance or recurrence.
Source control
Draining accumulating infected fluids and pus from abscesses or sites of infection is key. Devices like infected IVs and catheters must be removed. Dead or infected tissues may need debridement. This reduces the pathogen load.
Fluids and electrolyte management
IV fluids and electrolytes are given to restore hydration and blood pressure. Kidney function and electrolyte levels are monitored. Dialysis filters blood if kidney failure occurs.
Oxygenation
Mechanical ventilation and oxygenation supports breathing in respiratory infections. Lung-protective low tidal volume strategies are used in cases like Acute Respiratory Distress Syndrome or ARDS.
Nutrition
Meeting caloric, vitamin and mineral needs with dietary management or tube feeds helps maintain energy and strength.
Treating complications
Medications that improve heart function, reduce inflammation and fluid buildup in lungs or balance coagulation help tackle associated organ complications and keep them functioning.
Preventing secondary infections
Pneumonia vaccines, antifungals, ulcer prevention medicines and antibiotic prophylaxis prevent secondary infections that can worsen outcomes.
Recovery and Prognosis After Widespread Infection
With treatment, the infection gradually comes under control as measured by shrinking abscesses, reduced fever, improving lab markers and growing strength. But full recovery takes time depending on how widespread the infection was and its complications.
Regaining functioning
Mobilizing early helps rebuild muscle strength lost due to prolonged illness and bed rest. Physical, occupational and speech therapy facilitate recovery after critical illness. Nutrition is optimized to heal wounds and rebuild tissues.
Managing lingering effects
Fatigue, body aches, trouble concentrating, anxiety, irritability and sleep issues are common post-infection. Light exercise, stress management and pulmonary rehabilitation programs help manage ongoing effects on lungs, kidneys or heart function.
Rehabilitation
Inpatient rehabilitation focuses on improving capability for daily living activities like dressing, bathing and mobility. Outpatient programs continue strengthening and skills training. Counseling addresses psychosocial aspects of recovery.
Preventing recurrences
Steps like vaccinations, finishing antibiotic courses, optimal diabetes control, avoiding contacts during immunosuppression, practicing good hygiene and wound care help prevent repeat infections. Post-infection screening checks for lingering germs.
The prognosis depends on factors like how early treatment was started, the appropriateness of antibiotics, the strength of immune function and the presence of complications or lasting organ damage. Severe septic shock has mortality rates around 40%, highest in the elderly. With aggressive treatment, most people survive disseminated infections. But full recovery and regained quality of life may take months. Ongoing monitoring and proactive steps are key to prevent repeat infections.
Conclusion
Widespread invasive infection unleashes a systemic inflammatory response that can impact the function of virtually any organ. Prompt diagnosis and tailored antibiotic treatment, addressing infection sources, organ support and managing complications are crucial to survival and recovery. While severe sepsis can be life-threatening, early medical care and diligent follow-up helps most people stabilize, recuperate and restore their health after the body’s battle against rampant infection.