Tue Aug 29

I think I have the flu. Should I ask my GP for antivirals?

Written by: Lara Herrero, Research Leader in Virology and Infectious Disease, Griffith University

If you test positive for COVID and you’re eligible for antivirals, you’ll likely ask your GP for a script to protect you from severe disease.

Antivirals ^[1] are also available to fight influenza viruses, via a doctor’s prescription. But they have a mixed history, with their benefits at times overstated ^[2].

It can be difficult to get an appointment to see your GP. So when should you make the effort to see a GP for a prescription for influenza antivirals? And how effective are they?

What exactly is influenza?

The flu is primarily a viral infection of the respiratory system that can spread through sneezing, coughing, or touching contaminated objects then touching your nose or mouth.

Common symptoms include headache, sore throat, fever, runny or blocked nose and body aches that last a week or more.

Influenza is actually a group of viruses, divided into several sub-groups ^[4]. Flu A and B are the most common groups ^[5] that circulate in humans.

What are flu antivirals?

Influenza antivirals, target specific parts of the viral life cycle, which prevents the virus replicating and spreading.

Most flu antivirals target ^[6] neuraminidase, an important enzyme the virus uses to release itself from cells.

On the other hand, COVID antivirals work by inhibiting other parts of the viral life cycle involved in the virus replicating itself ^[7].

Three influenza antivirals are used in Australia ^[8]. Relenza (zanamivir) is an inhaled powder and Tamiflu (oseltamivir) is a capsule; both are five-day treatments. Rapivab (peramivir) is a single injection.

These antivirals may also come with side effects ^[9], such as a headache, vomiting, cough, or fever ^[10].

Tamiflu and Relenza generally cost A$40-50 in Australia, plus the cost of the consultation fee with your doctor, if applicable.

How effective are antivirals for the flu?

Antivirals have the greatest effect if started 24-72 hours after symptoms. This is to prevent the virus from reaching high levels in the body ^[12].

Among healthy adults, if Relenza or Tamiflu are started within 48 hours from your first symptoms, they can reduce the duration ^[13] of symptoms such as cough, blocked nose, sore throat, fatigue, headache, muscle pain and fever by just under a day.

For people who have developed severe flu symptoms or who have existing health conditions such as heart disease or chronic obstructive pulmonary disease (COPD), antivirals that start later (but still before day five of symptoms) can still reduce the severity of infection ^[14] and reduce the chance of ^[15] hospitalisation ^[16] and death ^[17].

Older man coughs, while his partner looks concerned

Antivirals need to be started early. Vlada Karpovich/Pexels ^[18]

In a study from the 2009 swine flu (H1N1) pandemic in the United States, treatment with antivirals (Tamiflu and Relenza) reduced ^[19] the chance of needing to be hospitalised. Around 60% of hospitalisations prevented were among 18-64 years olds, around 20% in children 0-17 years, and 20% in adults aged over 65.

The research is less clear about whether antivirals prevent the development of flu complications such as secondary bacterial pneumonia. They might, but so far the data aren’t clear.

Are flu antivirals becoming less effective?

Antiviral resistance to Tamiflu has been reported ^[20] around the world, mostly in immunocompromised people ^[21], as they have ^[22] a weakened immune system that allows higher viral loads and prolonged viral shedding.

The impact of the antiviral resistance is unclear but there is evidence indicating resistant strains can uphold their ability to replicate effectively and spread. So far it’s not clear if these stains cause more severe disease.

However, government agencies and surveillance programs are constantly monitoring the spread of antiviral resistance. Currently there is minimal concern ^[23] for strains that are resistant to Tamiflu or Relenza.

Antivirals can also prevent the flu if you’ve been exposed

Tamiflu and Relenza can also be used to prevent flu infections ^[25], if we’re exposed to the virus or come into contact with infected people.

Some studies suggest Tamiflu and Relenza can reduce the chance of developing symptomatic influenza ^[26] by 70-90%.

Many health agencies around the world recommend ^[27] “prophylactic” treatment for high-risk patients in hospitals or age care setting when people have been in contact with others infected with influenza.

Woman at supermarket reaches for an orange

Antivirals can stop people who have been exposed to influenza from developing severe illness. Anna Shvets/Pexels ^[28]

So who should talk to their GP about a prescription?

Australian guidelines recommend ^[29] doctors offer antivirals to people with influenza who have severe disease or complications.

Doctors can also consider treatment for people at higher risk of developing severe disease from influenza. This includes:

adults aged 65 years or older
pregnant women
people with certain chronic conditions (heart disease, Down syndrome, obesity, chronic respiratory conditions, severe neurological conditions)
people with compromised immunity
Aboriginal and Torres Strait Islander people
children aged five years or younger
residents of long-term residential facilities
homeless people.

Doctors can prescribe antivirals for the prevention of influenza in vulnerable people who have been exposed to the virus.

Antiviral treatment also can be considered ^[30] for otherwise healthy symptomatic patients who have confirmed or suspected influenza, if they can start treatment within 48 hours of developing symptoms.

In some instances a doctors can make a clinical diagnosis of influenza based on the symptoms and known close flu positive contacts of the patient. However, it is preferred to have flu diagnosed by one of the approved diagnostic tests, such as a rapid antigen test ^[31] (RAT) or the more accurate PCR test ^[32], similar to what is perfomed for COVID. There are also now combo tests that can distinguish between SARS-CoV-2 and influenza virus ^[33].

Remember, the flu can cause severe illness or death ^[34], particularly among people from the high-risk groups. So if you think you might have the flu, wear a mask and stay away to avoid spreading the virus to others.