Introduction
The flu is a term commonly used to describe illnesses caused by influenza viruses. This is a virus that can cause infection of the lungs, nose and throat.1 On the other hand, the term ‘stomach flu’ is used to describe gastroenteritis, which is an illness associated with infection of the intestines by bacteria, viruses, or parasites.2 This article will highlight the key differences in the causes and symptoms of both infectious diseases, as well as recommended treatments and prevention strategies for each disease.
Causes
Influenza is caused by influenza viruses, which attack the respiratory system. They can infect both humans and animals. The two most common types of influenza viruses that can cause infection in humans are Influenza A and Influenza B. Although the flu can occur throughout the year, influenza is known to cause seasonal flu, particularly in the winter season. Once the virus has entered the human body, it damages the cells in the lining of the nose, mouth and lungs, leading to infection.3
Influenza viruses have unique proteins on their surface. When these are recognised by our immune system, our body is able to identify and kill the infecting viruses. However, the virus is able to adapt and alter its surface proteins, making it harder for our immune systems to recognise its presence and allowing it to continue to circulate.4 This is why, whilst we have treatments and vaccines for influenza, the disease is still prevalent on a global scale, affecting both humans and animals.5
Gastroenteritis (or stomach flu) can be caused by a variety of different pathogens, including viruses, bacteria, or parasites. These pathogens cause the gastrointestinal tract to become inflamed, damaging the lining of the stomach and intestines.
If left untreated, gastroenteritis can lead to serious illness as a result of electrolyte imbalances and dehydration.6 It is important to understand which pathogen is causing the illness, as each will need to be treated differently. For example, antibiotics cannot treat viral gastroenteritis as they only treat bacterial infections.
Viral causes of gastroenteritis include norovirus, which most commonly affects adults, and rotavirus, which most commonly affects children. Common bacterial causes include Eschericha coli, Salmonella, and Campylobacter.7 Parasitic gastroenteritis is most commonly caused by cryptosporidium and giardia.8
Symptoms
One of the main ways to distinguish between influenza and gastroenteritis is via their symptoms. These diseases affect different areas of the body, and thus present differently. Influenza causes symptoms that primarily affect the respiratory tract, whilst gastroenteritis primarily targets the gastrointestinal tract.9,20
The table below shows the telltale signs of each sickness. However, it is important to note that influenza and gastroenteritis share some common symptoms, including headaches, fevers and chills. As such, it is important to recognise specific symptoms, such as coughs and diarrhoea which clearly set these illnesses apart.
Table 1
Common Influenza Symptoms | Low-grade fever |
Cough | Nausea/vomiting |
High fever | Diarrhoea |
Body aches and headaches | Abdominal cramps |
Sore throat | Suppressed appetite |
Runny/stuffy nose | Low grade fever |
Transmission
Influenza virus is spread from person to person through respiratory droplets. This transmission occurs through droplets in the air when a person coughs, sneezes, or when a person is talking. These droplets contain the virus or viral particles and can be inhaled by healthy individuals nearby. Once the droplets enter the nose or mouth, the virus can make its way to the lungs and begin to cause infection.14
Gastroenteritis can be spread through food, water or faecal-oral transmission. Foodborne transmission refers to the spread of disease through contaminated foods. Common risk factors include eating food that has not been washed, cooked, or prepared properly, as well as eating or drinking unpasteurized products. Improper or incomplete food preparation allows bacteria to grow on the food and enter our bodies when we eat it.
Waterborne illness refers to transmission through the consumption of contaminated water or liquids - for example, drinking unfiltered, unclean water or swimming or bathing in contaminated pool, shower, or bath water.
Faecal-oral transmission refers to when individuals inhale or otherwise ingest pathogen-containing particles from an infected individual’s vomit or excretion.15 This can occur when proper hygiene and sanitation methods, such as hand washing, are not followed. These pathogens are so small that it is unclear whether something entering your mouth could contain them, so it is always important to be mindful of risk factors and follow basic hygiene protocols.
Timeframe of disease
The incubation period is the time between an individual becoming infected with a disease to the individual developing the symptoms associated with it.
The average incubation period for influenza tends to be around two days. It is important to note that whilst this is an average, every individual is different and some people may have a longer incubation period. Symptoms can also vary from mild such as light headaches or light cough, to severe symptoms requiring bed rest and/or further treatment.1
The average incubation period for Gastroenteritis tends to range from one to three days. Once the pathogen infects someone, it can take over 24 hours for symptoms to appear, with early symptoms including loss of appetite and abdominal cramps. These are followed by vomiting and/or watery diarrhoea.11 It is important to keep hydrated, as loss of electrolytes can lead to serious illness requiring hospital attention.
The duration of illness refers to the period in which an infected individual remains symptomatic.
In typical cases, influenza symptoms tend to last around three to seven days. The human immune system can usually clear the infection itself. However, influenza can sometimes cause more complicated illnesses that require medical attention. These are more common in people over 65, young children, or individuals with underlying health conditions that may compromise their immune systems.12 Possible complications include pneumonia, sinus infections, ear infections, or bronchitis, which may be the result of secondary infection with a bacterial pathogen after viral infection.
The typical duration of Gastroenteritis can be from two days to two weeks depending on the severity of the infection.10 The human immune system is often able to recognise and fight off viral or bacterial pathogens quickly. When the immune system recognises these pathogens, it is able to neutralise them or expel them from the body.
Vomiting and diarrhoea are both ways in which the body aims to expel the pathogen.16 However, when symptoms are still present after a few days, it is recommended to seek medical attention as this is a sign of a more severe form of gastroenteritis.
Treatment
It is important to stay at home as much as possible to allow your body the best chance at recovery and minimise the risk of spreading the disease to others. Here are some tips on how to manage and deal with the illness at home:
Influenza
- Painkillers: ibuprofen or paracetamol can provide relief from headaches or achy limbs
- Rest: allow your body to sleep in order to help it fight infection
- Warm liquids: liquids containing natural herbs like liquorice root and elderberry can help relieve a sore throat18
- Steam: using hot steam, such as in a bath or shower, can help relieve nasal infections
Gastroenteritis
- Hydration: drinking plenty of fluid is crucial to managing gastroenteritis. Taking slow sips with a straw can help keep fluids down19
- Simple foods: ease back into eating by consuming plain foods such as yoghurt, toast, cereals, fruit, and vegetables. Avoid spicy and high fat foods which may aggravate your stomach, making symptoms worse
- Herbal teas: teas containing ginger, cinnamon and turmeric are known for relieving discomfort
- Zinc: zinc supplements can help boost your immune system for a smoother and faster recovery18
Whilst home remedies and tips can help with relief of symptoms, you should seek medical advice if your illness passes the typical incubation period or you have severe symptoms.
Prevention
Prevention of disease is vital in minimising the number of people becoming ill. In general, basic means of disease prevention include following good hygiene and sanitation practices. For influenza, this refers to hand washing, wearing a facial mask whilst symptomatic, and following regular cleaning and social distancing protocols.
For gastroenteritis, hand washing and using the correct bacterial and viral killing products when cleaning up vomit or diarrhoea is crucial. On top of this, thorough cleaning and proper cooking of food is also important to prevent disease.13
Flu vaccination
Influenza is highly contagious and it remains a global health issue due to its ability to change and adapt its surface proteins. The surface proteins usually allow our immune systems to recognise the pathogen and trigger an immune response to fight infection.
Whilst the flu vaccine can prevent influenza or decrease severity of symptoms, a new vaccine is produced every year to accommodate the possible changes to the influenza viral proteins.17 This is why it is recommended you get a new flu vaccination every year, so that your body is able to recognise the new form of the virus.
Summary
Influenza and gastroenteritis are both types of flu, but they manifest differently in the body. Influenza is a viral infection that affects the respiratory tract and causes symptoms such as fevers, chills, and coughing. On the other hand, gastroenteritis can be caused by a variety of pathogens, which attack the gastrointestinal tract and cause vomiting and diarrhoea.
While both illnesses can be tackled by the immune system, severe cases require medical attention to prevent potentially life-threatening secondary infections. Emphasising basic preventative measures, including increased hygiene and sanitation protocols, is crucial in managing the spread of these diseases. Additionally, individuals at high risk should promptly seek medical advice if infected, and keep up with their yearly flu vaccinations to prevent catching seasonal influenza.
References
- NHS. Flu [Internet]. NHS. 2022 [cited 2024 Apr 27]. Available from: https://www.nhs.uk/conditions/flu/
- Balsalobre-Arenas L, Alarcón-Cavero T. Rapid diagnosis of gastrointestinal tract infections due to parasites, viruses, and bacteria. Enfermedades infecciosas y microbiologia clinica (English ed). 2017;35(6):367–76.
- CDC. Understanding Influenza Viruses [Internet]. 2019 [cited 2024 Apr 27]. Available from: https://www.cdc.gov/flu/about/viruses/index.htm
- Neverov AD, Kryazhimskiy S, Plotkin JB, Bazykin GA. Coordinated Evolution of Influenza A Surface Proteins. PLOS Genetics. 2015;11(8):e1005404.
- CDC. How the flu virus can change: “Drift” and “shift” [Internet]. 2019 [cited 2024 Apr 27]. Available from: https://www.cdc.gov/flu/about/viruses/change.htm
- Merck Manuals Consumer Version. Overview of Gastroenteritis - Digestive Disorders [Internet]. [cited 2024 Apr 27]. Available from: https://www.merckmanuals.com/home/digestive-disorders/gastroenteritis/overview-of-gastroenteritis
- NHS Inform. Escherichia coli (E. coli) O157 symptoms and treatment [Internet]. 2023 [cited 2024 Apr 27]. Available from: https://www.nhsinform.scot/illnesses-and-conditions/infections-and-poisoning/escherichia-coli-e-coli-o157
- Moro DD, David MO. Infectious Gastroenteritis: Causes, Diagnosis, Treatment and Prevention. CGH [Internet]. 2019 [cited 26 Jun 2024] ;2(5):194–7. Available from: https://lupinepublishers.com/gastroenterology-hepatology-journal/fulltext/infectious-gastroenteritis-causes-diagnosis-treatment-and-prevention.ID.000147.php
- Tamura S, Takeshi K. “Defense Mechanisms against Influenza Virus Infection in the Respiratory Tract Mucosa.” JJID. 2004;57:236-247.
- Lee RM, Lessler J, Lee RA, Rudolph KE, Reich NG, Perl TM, et al. Incubation periods of viral gastroenteritis: a systematic review. BMC Infect. Dis. 2013;13:446.
- Hopkins Medicine. Understanding Viral Gastroenteritis [Internet]. 2019 [cited 2024 Apr 27]. Available from: https://www.hopkinsmedicine.org/health/conditions-and-diseases/understanding-viral-gastroenteritis#:~:text=A%20virus%20causes%20this%20illness.%20It%20can%20infect
- CDC. People at High Risk For Flu Complications [Internet]. 2018 [cited 2024 Apr 27]. Available from: https://www.cdc.gov/flu/highrisk/index.htm
- Yale Medicine. Gastroenteritis [Internet]. [cited 2024 Apr 27] Available from: https://www.yalemedicine.org/conditions/gastroenteritis
- Brankston G, Gitterman L, Hirji Z, Lemieux C, Gardam M. Transmission of influenza A in human beings. Lancet Infect. Dis. 2007 Apr;7(4):257–65.
- Gordon I, Ingraham HS, Korns RF. TRANSMISSION OF EPIDEMIC GASTROENTERITIS TO HUMAN VOLUNTEERS BY ORAL ADMINISTRATION OF FECAL FILTRATES. JEM. 1947;86(5):409–22.
- Axelrad JE, Cadwell KH, Colombel JF, Shah SC. The role of gastrointestinal pathogens in inflammatory bowel disease: a systematic review. Therap. Adv. Gastroenterol. 2021 Jan;14:175628482110044.
- Yoshino Y, Wakabayashi Y, Kitazawa T. The Clinical Effect of Seasonal Flu Vaccination on Health-Related Quality of Life. Int. J. Gen. Med. [Internet]. 2021;14:2095–9. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8166814/
- Mousa HAL. Prevention and Treatment of Influenza, Influenza-Like Illness, and Common Cold by Herbal, Complementary, and Natural Therapies. J. Evid. Based Complementary Altern. Med. 2016 Jun 22;22(1):166–74.
- NHS. Diarrhoea and Vomiting [Internet]. 2020 Dec 7 [cited 2024 Apr 27]. Available from: www.nhs.uk/conditions/diarrhoea-and-vomiting/.
- Duncan DL. Gastroenteritis: An overview of the symptoms, transmission and management. Br. J. Sch. Nurs. 2018;13(10):484–8.