The appearance of blood in respiratory discharge, often referred to as bloody mucus or hemoptysis, can be an alarming symptom, especially during a viral outbreak. This discharge may originate from the nose, throat, or lungs, causing concern about the severity of an underlying illness. Given the respiratory nature of the SARS-CoV-2 infection, people often question the link between the virus and this specific manifestation. This article explores the relationship between COVID-19 infection and the presence of blood in respiratory secretions.
Is Bloody Mucus a Direct Symptom of COVID-19?
Bloody mucus can be a symptom of COVID-19, but it is considered an uncommon occurrence compared to symptoms like fever, cough, and fatigue. Clinical observations indicated that hemoptysis, or coughing up blood, occurred in a small percentage of cases. Reports on the prevalence of this symptom typically place it in the range of 0% to 5% among COVID-19 patients.
When blood is present, it is far more frequently seen in individuals experiencing a severe or advanced stage of the disease. It is noted more often in critically ill patients who require mechanical ventilation or other advanced support. While documentation confirms the possibility of this symptom during a SARS-CoV-2 infection, it is not a defining characteristic of a typical, uncomplicated case.
Physiological Causes of Blood in Respiratory Discharge
The presence of blood in the mucus during a COVID-19 infection is linked to several biological and mechanical processes within the respiratory system. A primary mechanism is the physical trauma caused by a persistent, aggressive cough, which is common with the infection. The force of violent coughing can severely irritate the lining of the trachea and bronchi, leading to micro-tears in the delicate tissues and small blood vessels.
Beyond mechanical irritation, the virus itself can directly affect the vascular system. SARS-CoV-2 is known to target and damage the vascular endothelium, the specialized cells that line the interior surface of blood vessels. This injury increases the fragility and permeability of the vessel walls, making them more prone to bleeding into the surrounding tissue and respiratory secretions.
COVID-19 infection can also induce a hypercoagulable or “prothrombotic” state, meaning the blood is more likely to clot. This can lead to the formation of microthrombi, or small blood clots, throughout the lungs, and sometimes, the development of pulmonary thromboembolism. These severe complications related to clotting and associated lung damage can directly result in the coughing up of blood. Inflammation and damage to lung tissue, such as viral pneumonia, also contribute significantly to the bleeding seen in more serious cases.
Distinguishing Between Common and Serious Causes
When streaks of blood appear in mucus, it is important to distinguish between minor irritation and a more serious underlying condition, regardless of COVID-19 status. Small amounts of blood can often be attributed to common, non-viral factors that irritate the upper respiratory tract. These include extremely dry air, which can crack the delicate nasal and sinus linings, or the physical stress of vigorous nose blowing.
Minor blood streaks may also occur due to a severe upper respiratory infection or acute bronchitis, where persistent coughing has irritated the airway, causing minor surface bleeding. If the bleeding is minimal, such as small flecks or streaks mixed with phlegm, it may resolve on its own as the irritation subsides.
The presence of blood can also signal a medical situation that requires immediate attention. It is a sign of concern if a person coughs up a significant volume of blood, particularly if it is bright red and frothy, which indicates it is coming from the lower airways. Emergency medical care should be sought if the bleeding is persistent, or if it is accompanied by other severe symptoms. These symptoms include difficulty breathing, rapid heart rate, chest pain, or a sudden deterioration in overall condition. Massive hemoptysis, typically defined as coughing up 300 to 600 milliliters of blood over 24 hours, is considered a life-threatening emergency.