Introduction

Influenza, which is commonly known as the flu, is a highly contagious viral infection that affects the respiratory system. Winter is the peak season for influenza viruses, causing illness in millions of people worldwide. While most people recover from the flu without complications, certain groups of people, such as the elderly, young children, and people with underlying health problems, are at higher risk of developing serious complications. One such complication that has attracted attention in recent years is the association between influenza and kidney disease.^1,2

Understanding influenza

Influenza viruses belong to the Orthomyxoviridae family, which are a class of negative-sense RNA viruses. They are divided into four main types: A, B, C and D.³ Influenza A and B viruses are responsible for seasonal outbreaks of influenza, with A viruses being the most common. Type A viruses have the widest host range, with common hosts including pigs, humans, cats, dogs, and poultry, in addition to humans.⁴ In addition to being the most prevalent type of influenza, influenza A is also the type of influenza with the highest risk of severe illness and mortality. Influenza B viruses are usually hosted by humans or pigs and can cause mild to severe illness. Influenza C viruses, on the other hand, usually cause milder respiratory symptoms.³ Type D viruses were discovered in 2011, but have not been found to be associated with clinical symptoms in humans.⁵

Symptoms of influenza include fever, cough, sore throat, muscle aches, fatigue, and headache. 

It is mainly spread through respiratory droplets produced when an infected person coughs or sneezes. Influenza can affect people of all ages, but certain groups of people are at higher risk for complications. These include the elderly, young children, pregnant women, people who are immunocompromised, and people with underlying medical conditions such as heart disease, lung disease, diabetes, and kidney disease.⁴

Overview of kidney disease

Kidney disease, also known as nephropathy, refers to a variety of disorders that affect the structure and function of the kidneys. There are two main types of kidney disease: acute kidney injury (AKI) and chronic kidney disease (CKD). Acute kidney injury (AKI) refers to the sudden loss of kidney function, which can be caused by a variety of factors such as infection, dehydration, drug toxicity and reduced renal blood flow.⁶ On the other hand, chronic renal failure is a progressive disease characterised by a gradual loss of kidney function over time. Clinical indicators are a glomerular filtration rate (GFR) of less than 60 mL/min per 1-73 m 2, or markers of renal damage lasting at least 3 months.⁶

Common causes of kidney disease include diabetes, hypertension, glomerulonephritis, polycystic kidneys and autoimmune diseases such as lupus. People with kidney disease may experience symptoms such as fatigue, swelling, changes in urine output and difficulty concentrating. If left untreated, kidney disease can progress to end-stage renal disease (ESRD), which requires dialysis or a kidney transplant to survive.⁷

The relationship between influenza and kidney disease

Several studies have investigated the relationship between influenza and kidney disease, and there is growing evidence that influenza infection can lead to kidney complications.^1,2 A study published in the Journal of the American Society of Nephrology found that influenza infection was associated with a significantly increased risk of developing acute kidney injury, particularly in older adults and those with pre-existing chronic kidney disease. In addition to this, the study also showed a 50% mortality rate in patients with influenza A and AKI who required dialysis.⁸

The exact mechanism by which influenza causes kidney injury is not fully understood, but several factors may contribute to the association. For example, influenza infection can lead to systemic inflammation and immune dysregulation, which in turn can damage the kidneys. In addition, certain strains of influenza (e.g., influenza A H1N1 strains) have been associated with more severe renal complications.⁶

Management of influenza in patients with renal disease

The prevention and control of influenza in patients with kidney disease is essential to reduce the risk of complications. Receiving a vaccination is the most effective way to prevent influenza and its associated complications. Influenza vaccination is recommended for all individuals aged 6 months and older, including those with underlying medical conditions such as kidney disease.

Besides vaccination, people with kidney disease should take other precautions to reduce the risk of influenza, such as maintaining hand hygiene, avoiding close contact with infected people, and staying at home when they are sick. If influenza is suspected or diagnosed in patients with kidney disease, prompt antiviral treatment is recommended to reduce the severity and duration of symptoms.⁹

FAQs

What is influenza and how does it relate to kidney disease?

Influenza, commonly known as the flu, is a contagious viral infection that primarily affects the respiratory system. While most people recover from the flu without complications, individuals with underlying health conditions, such as kidney disease, are at higher risk of developing serious complications. Studies have shown a significant association between influenza infection and kidney complications, including acute kidney injury (AKI) and worsening of chronic kidney disease (CKD).

What are the symptoms of influenza?

Symptoms of influenza include fever, cough, sore throat, muscle aches, fatigue, and headache. It is primarily spread through respiratory droplets produced when an infected person coughs or sneezes. Individuals with kidney disease may experience more severe symptoms and are at increased risk of developing complications from influenza.

What are the types of influenza viruses?

Influenza viruses are classified into four main types: A, B, C, and D. Influenza A and B viruses are responsible for seasonal outbreaks of the flu, with type A viruses being the most common and posing the highest risk of severe illness. Influenza C viruses typically cause milder respiratory symptoms, while type D viruses have not been found to be associated with clinical symptoms in humans.

How does influenza affect individuals with kidney disease?

Individuals with kidney disease, especially those with pre-existing chronic kidney disease (CKD), are at higher risk of developing acute kidney injury (AKI) during influenza infection. Influenza can exacerbate kidney disease and lead to complications such as fluid overload, electrolyte imbalances, and the need for dialysis. Prompt diagnosis and treatment of influenza in patients with kidney disease are essential to prevent further kidney damage.

How can influenza be managed in patients with kidney disease?

Preventing and managing influenza in patients with kidney disease is crucial to reduce the risk of complications. Vaccination is the most effective way to prevent influenza and its associated complications in this population. In addition to vaccination, individuals with kidney disease should practice good hand hygiene, avoid close contact with infected individuals, and stay home when sick. Prompt antiviral treatment may be recommended for patients with kidney disease who develop influenza to reduce the severity and duration of symptoms.

What should individuals with kidney disease do during flu season?

During flu season, individuals with kidney disease should take proactive measures to protect themselves from influenza. This includes getting vaccinated against the flu, practising good hygiene, avoiding close contact with sick individuals, and seeking prompt medical attention if flu-like symptoms develop. It is essential for individuals with kidney disease to work closely with their healthcare providers to develop a personalised plan for flu prevention and management.

Summary

Influenza, commonly known as the flu, is a highly contagious viral infection that affects the respiratory system. Influenza viruses belong to the Orthomyxoviridae family and are divided into four main types.

Symptoms of influenza include fever, cough, sore throat, muscle aches, fatigue and headache. It is spread primarily through respiratory droplets produced when an infected person coughs or sneezes. While most people recover from the flu without complications, certain groups of people, such as the elderly, young children, and people with underlying health problems, are at higher risk for serious complications. Recent studies have shown that people with underlying medical conditions, such as kidney disease, are at a higher risk of developing complications from the flu.

Kidney disease, or nephropathy, refers to a variety of conditions affecting kidney structure and function. There are two main types of kidney disease: acute kidney injury (AKI) and chronic kidney disease (CKD). AKI is the sudden loss of kidney function and can be caused by factors such as infection, dehydration, drug toxicity and reduced renal blood flow. CKD is a progressive disease characterised by a gradual loss of kidney function over time.

Emerging research has linked influenza infection to complications in patients with kidney disease, making the prevention of influenza in these patients essential. Vaccination is the most effective way to prevent influenza and its associated complications. In addition to vaccination, patients with kidney disease should take other precautions to reduce their risk of influenza, such as maintaining hand hygiene, avoiding close contact with sick people, and staying home when sick. For kidney disease patients who develop flu symptoms, prompt antiviral treatment is recommended to reduce the severity and duration of symptoms.