Article
Source: Campus Sanofi
23 Oct 2023

2 min

Burden of Influenza

Author: Sanofi

Editorial team

Every year, millions of cases of influenza are recorded worldwide.

What is the burden of influenza for at-risk patients?

Some people may be at increased risk of influenza-related complications, including:¹

Adults aged 65 + years

Those with underlying health conditions

Chronic respiratory conditions

Patients with chronic respiratory conditions may be at increased risk of serious flu-related complications.¹ This is because flu is a respiratory virus that can make existing breathing conditions worse by putting extra strain on the lungs.⁴ A respiratory condition may also limit the types of medicines that can be given to treat flu in these patients, potentially causing longer recovery times and a need for hospitalisation.⁴

Chronic heart conditions

Patients with chronic heart conditions may be at increased risk of serious flu-related complications.⁵ Flu complications can be severe for patients with heart disease and can lead to considerable morbidity and mortality.^6,7

Chronic kidney disease

Patients with chronic kidney disease (CKD) may be at increased risk of serious flu-related complications due to the immune dysfunction that accompanies this condition.^8,9 CKD may also increase the risk of mortality for patients compared with healthy people.¹⁰

Chronic liver conditions

Patients with chronic liver disease may be at increased risk of serious flu-related complications due to the immune dysfunction that accompanies this condition.^11,12 These complications may also increase the risk of mortality in patients.¹² Chronic liver conditions may limit the types of medicines that can be given to treat flu, potentially causing longer recovery times and the need for hospitalisation.¹³

Chronic neurological conditions

Patients with a chronic neurological condition may be at increased risk of serious flu-related complications.^1,14 Flu can worsen existing neurological symptoms, for example difficulty breathing, or regulating body temperature. This can lead to other complications, such as pneumonia, and increase the risk of hospitalisation.¹⁴ Studies have also shown that flu can cause a relapse in one third of patients with multiple sclerosis within 6 weeks.¹⁴

Diabetes

Patients with diabetes may be at increased risk of serious flu-related complications, for example pneumonia.^15,16 Flu may increase a patient’s blood sugar levels, which can lead to diabetic complications including ketoacidosis and hyperglycaemic hyperosmolar non-ketotic coma.¹⁷ Flu-related challenges in managing blood sugar levels may also slow diabetic patients’ recovery time from flu.¹⁶

Immunosuppression

Patients who are immunosuppressed may be at increased risk of flu-related complications.¹ These may include lower respiratory tract infections, and in some unusual manifestations, rhabdomyolysis and myocarditis.¹⁸ As a result of these complications, those who are immunosuppressed may also have a higher risk of mortality and morbidity from flu.^1,19

Asplenia or dysfunction of the spleen

Patients with asplenia (an absent or dysfunctional spleen [including conditions like sickle cell and coeliac disease), may be at increased risk of certain infections, such as flu,²⁰ due to an impaired immune system.²¹ The spleen helps fight invading pathogens in the blood, with the help of white blood cells.²¹ When the spleen is not working properly, patients may be less able to tackle infections like flu.²¹

Morbid obesity (BMI ≥40 kg/m²)

Adults with a body mass index (BMI) of ≥40 kg/m² may be at increased risk of flu-related complications.^1,22 These may include pneumonia and damage to the lungs and could increase the need for hospitalisation.²³ In some cases, these flu-related complications may also be linked to a higher risk of mortality.²³ Many patients in this group may already be eligible for a flu vaccination, due to complications of obesity that put them in another at-risk group.¹

Pregnant women

Babies and children

Flu vaccination is an essential part of helping protect communities²⁹

The Health Circle Podcast

Learn more about influenza vaccination in our podcast The Health Circle. In each episode, we explore a new topic related to flu vaccination.

Overview of the UK Influenza National Programme

Influenza Vaccination for Pregnant Women

Influenza Vaccination for Over 65s

Influenza Vaccination for At-risk Groups

What are the complications associated with the burden of Influenza?

Influenza may trigger other unwanted health complications for patients

Evidence indicates that influenza may trigger severe cardiovascular complications beyond respiratory infection.⁷

A self-controlled case series study conducted in Scotland showed that adults aged 40 years and older (median age 68), without a history of heart attack or stroke, were at a significantly increased risk of severe cardiovascular complications in the 1–3 days following a confirmed influenza infection.⁷

In the 1–3 days following a laboratory-confirmed influenza infection:^a

Risk of having a heart attack⁷

Risk of having a stroke⁷

^aIn a self-controlled case series study (based on a population in Scotland 2004-2014) conducted on a database of adults aged ≥ 40 years with ~90% of the study population aged 50 years and older. In the 1–3 days following a laboratory-confirmed influenza infection versus unexpected or baseline time periods.

CI, confidence interval; IR, incidence ratio.

Hospitalisations and economic burden of influenza

Influenza has an associated impact on healthcare costs and resources.

Influenza may have a considerable burden on secondary healthcare systems.³⁰

Hospital admissions during the 2018/19 influenza season had associated medical costs of £99,565,310.¹ The highest costs were found to be associated with patients aged 65+ years.³⁰

Certain groups may create increased pressure as they are more likely to experience a longer and more severe illness. During the 2018/19 influenza season:³⁰

<65 years	75+ years
Costs per hospitalisation: ~£1,900	Costs per hospitalisation: ~£3,700
Average length of stay: 4.74 days	Average length of stay: 12.55 days
Mortality: 1.83%	Mortality: 11.18%

References

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MAT-XU-2301387 (v2.0) Date of preparation: October 2023