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Can you get influenza A twice

Can You Get Influenza A Twice?

, by AussiePharmaDirect, 7 min reading time

Notably, influenza A viruses have been associated with significant pandemics that have had far-reaching consequences. The most well-known example is the 1918 influenza pandemic, often referred to as the "Spanish flu," which infected millions of people worldwide and resulted in a high mortality rate. In more recent times, influenza A subtypes have caused other notable pandemics, including the 2009 H1N1 "swine flu" pandemic and avian influenza (H5N1) outbreaks.

The genetic makeup of influenza A plays a significant role in its ability to cause pandemics. Influenza A is a virus that possesses two crucial surface proteins, hemagglutinin (HA) and neuraminidase (NA), which exist in different combinations. These proteins act as the virus's disguise, enabling it to infiltrate and infect our respiratory cells. Because of this, there is that big question that we’ve all been thinking of: Can you catch influenza A twice in a short span? Or even later down the line?

Our blog has the inside scoop on this captivating question. We'll delve into how our immune responses to the virus, the influenza A virus variations, and the ever-elusive concept of immunity.

Signs of influenza A

When a person is infected with influenza A, they may experience a range of signs and symptoms. Here are some common indicators of influenza A infection:

  • High fever, typically above 100.4°F (38°C)
  • Body aches and muscle pain
  • Fatigue and weakness
  • Dry cough, often accompanied by a sore throat
  • Headache
  • Nasal congestion or runny nose
  • Sudden chills
  • Chest discomfort or tightness, particularly in individuals with underlying respiratory conditions
  • Sneezing

How long is influenza A contagious?

Influenza A is generally considered contagious starting from one day before symptoms appear and can continue to be contagious for up to 5 to 7 days after the onset of symptoms.

Are you immune to the flu after having it?

Having a previous flu infection can provide some level of immunity against that specific strain of the influenza virus. When a person is infected with a particular strain of Influenza A, their immune system springs into action, mounting a defence to combat the invader.

Here's the remarkable part: once the immune system has successfully fought off a specific strain of Influenza A, it retains a memory of that encounter. It remembers the specific characteristics of the virus and keeps a blueprint for producing the corresponding antibodies. This immune memory provides protection against future infections with the same strain.

Additionally, the duration of immunity following a flu infection can vary. Some individuals may have longer-lasting immunity, while others may experience a decline in immunity over time. However, it's important to note that the immune response and the protection it offers are specific to the strain encountered previously. Influenza A is notorious for its ability to mutate and change its surface proteins through antigenic drift and shift. When a new strain of influenza emerges, the immune system may not have the specific antibodies required for efficient neutralisation.

Can you get influenza A twice in a month?

It is possible to get infected with Influenza A more than once within a short span of time, including within a month. While previous infection with Influenza A can provide some level of immunity against the specific strain encountered, it does not guarantee lifelong protection against all strains of the virus.

Influenza, being a seasonal virus, demonstrates a fascinating pattern of circulation that varies from year to year. The seasonal nature of influenza is driven by several factors, including changes in environmental conditions, human behaviour, and the characteristics of the virus itself. This results in different strains of influenza circulating during different flu seasons.

The most common subtypes of influenza A that infect humans are A(H1N1) and A(H3N2). Especially with Influenza A, it is known for its ability to undergo genetic mutations and reassortment, leading to the emergence of new strains. So, even if someone has previously been infected with one strain of Influenza A (for example the H3N2), they may still be susceptible to other strains, such as the H1N1 strain or even the Influenza B virus that may emerge in subsequent flu seasons.

Who is the most at risk for reinfection?

While anyone can be at risk for reinfection with Influenza A, certain groups may have a higher susceptibility. These include:

  1. Immunocompromised individuals: People with weakened immune systems, such as those undergoing chemotherapy, organ transplant recipients, or individuals with certain medical conditions (e.g., HIV/AIDS).
  2. Elderly individuals: Older adults, particularly those over the age of 65, may have an age-related decline in immune function, known as immunosenescence. 
  3. Young children: Children, especially those under the age of 5, have developing immune systems that may not provide robust and long-lasting immunity against Influenza A. They can be at an increased risk of reinfection, particularly if they have not received the recommended flu vaccinations.
  4. Healthcare workers: Individuals working in healthcare settings, who come into close contact with infected patients, may face a higher risk of exposure to different strains of Influenza A.
  5. Individuals with repeated exposure: People who have frequent exposure to the influenza virus, such as those living in close quarters (e.g., college dormitories, military barracks) or individuals who work in crowded environments, may have a higher risk of reinfection due to ongoing exposure to different strains.

How do I reduce the risk of contracting influenza?

If you’ve been wondering if you should get a flu vaccination, it is still considered one of the important preventive measures for influenza. While the flu vaccine does not provide 100% immunity against all strains of influenza, it plays a crucial role in essentially priming your immune system to respond more effectively to the influenza virus, reducing the likelihood of getting sick or experiencing severe symptoms. It is important to note that the flu vaccine is updated annually to match the circulating strains of influenza viruses expected for the upcoming flu season. 

Additionally, practising good respiratory and hand hygiene, avoiding close contact with sick individuals, practising an active lifestyle and healthy diet, taking supplements (for those with nutrient deficiency), and following public health guidelines can further minimise the risk of reinfection. 



Reinfection with influenza A is still possible due to several factors. While previous infection with influenza A may provide some level of immunity, it does not guarantee lifelong protection against all strains of the virus. 

If you develop symptoms but are still unsure if you are just having a common cold, influenza or COVID-19 because of the similar symptoms associated with the illnesses, you can always use the 3-in-1 antigen test kit for detection to help you better understand your condition. However, if your condition worsens, or if you have underlying health conditions that put you at higher risk, it is crucial to seek medical advice promptly.


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