The cold season is once again upon us and with this comes the worry of catching the flu. Flu, or influenza, is a viral infection that can affect our respiratory system starting from the nose, throat, and down to the lungs. This is a common disease and symptoms can range from mild to severe. So we ask, what exactly is influenza?
There are four known types of influenza viruses: A, B, C, and D. Of these four, A, B, and C are capable of infecting humans. Influenza A and B are usually responsible for the seasonal epidemics but Influenza A is more virulent and mutates faster, thereby making it capable of causing pandemics. The recent flu pandemics are caused by strains of Influenza A: H3N2 (1968), H5N1 (2004), and H1N1 (2009). This is the reason why vaccines and previous natural infection with influenza do not confer lifelong immunity – the virus mutates so fast that it escapes detection.
How does it spread?
Influenza can spread fast because it can be transmitted in three ways:
- Direct transmission – This happens through kissing or when an infected person sneezes or coughs directly into the eyes, nose or mouth of another person.
- Airborne transmission – This occurs when the infectious particles are propelled in the air when someone coughs, sneezes or spits.
- Contact with fomites – Fomites are objects that were touched by an infected person and have been contaminated with the virus (doorknob, money, phone, etc.). Depending on the surface material, the virus can persist for a variable amount of time (minutes to days).
Children are also a big factor in facilitating community outbreaks as they are not as conscious with hand hygiene and cough etiquettes.
What are the signs and symptoms?
The flu can manifest as a mild illness or can be severe and life-threatening. Mild cases of flu can be difficult to differentiate from the common cough and colds. Sometimes, it can involve various organs of the body as described below:
High-grade fever and chills
Muscle or joint pains
Cough, sore throat, runny nose, and increase in respiratory rate
Symptoms can last for 2-5 days but viral shedding, especially in children, can last for several weeks. Secondary bacterial infections may occur such as middle ear infections, sinusitis or pneumonia.
How is it diagnosed?
Most people are not tested for flu and are diagnosed based on characteristic symptoms. Respiratory secretions can be sent to the lab for culture or assay but their use in our country is limited by availability and cost. Complete blood counts (CBCs) and chest x-rays usually show non-specific results.
How is it treated?
The treatment of influenza is usually supportive: lots of fluids, rest and staying away from tobacco and alcoholic beverages. Paracetamol can be taken for fever and body pain. It is important to note that aspirin should be avoided because it can cause serious liver complications. Antiviral medications, when given early, can lessen symptoms and shorten the course of illness by 1-2 days. On the other hand, antibiotics are not recommended unless there is an ongoing simultaneous bacterial infection.
How do we avoid getting the flu?
According to the Center for Disease Control and Prevention (CDC), the most important step in preventing this disease is through appropriate vaccination. Because there are different kinds of flu viruses which are capable of mutating, the composition of flu vaccines is reviewed and updated annually to correspond to the currently circulating flu viruses. Experts recommend getting your shot before the flu season begins to give your body time to develop antibodies.
Moreover, personal habits can help prevent the spread of flu and other diseases. These include hand washing, good personal hygiene, staying away from sick people, and likewise staying away from others when you are sick.
As mentioned, the virus mutates fast. Because of this, researchers are constantly on the lookout for alternative ways to prevent this common illness. Antiviral drugs like amantadine and rimantadine have been studied for the prevention of Influenza A. Because their efficacy as prophylactic drugs is low, their use is limited only when there is a high probability of an epidemic or pandemic.