It's that time of year again, flu season is just around the corner and with it comes the dreaded fear of catching the virus. The flu can come on very quickly and symptoms include aching muscles, chills and sweats, a persistent headache as well as a dry, cough - along with fatigue and weakness.
The flu vaccine becomes available just before the flu season starts - which is April to September in the southern hemisphere, October to April in the northern hemisphere, and throughout the year in the tropics. For children, the nasal vaccine contains weakened live viruses while for adults the injected flu vaccine contains inactivated flu viruses. The vaccine cannot cause flu but it activates the immune system to initiate enough protection in case the influenza infection strikes.
It isn't possible to predict the number of cases or the exact month when the flu season will hit in the UK. But flu generally circulates during winter and peaks in December and January. Though there have been alarming reports earlier in the year from Australia where more than 301,118 cases of flu were confirmed plus 662 flu related deaths. This is much higher than the previous five-year average of around 110,000 in a season - and may be a sign of what is to come over the winter months in the UK.
Asthma and the flu
In healthy people flu usually clears up on its own within a week, but it can cause severe illness, complications and even death among vulnerable people - this includes older people, pregnant women and people with an underlying health condition. These people are advised to have a flu vaccine each year.
Most asthmatics are entitled to a free flu jab on the NHS as they are classed as a vulnerable group - but not everyone takes up the offer. This is despite the fact that people with asthma - both adults and children - are more prone to develop pneumonia after the flu.
The consequences of flu infection are much worse in asthmatics. This is in part because the flu virus causes inflammation in the respiratory system - which not only triggers symptoms of asthma -- shortness of breath, wheezing and chest tightness -- but also makes those symptoms much more of an issue.
The reason why people with asthma show such a severe response to influenza is not fully understood. But the fact that the airways of people with asthma are different compared to the airways of healthy people, plays a big part.
In asthmatics, the airways have larger smooth muscles - which help to control the flow of air - and this can cause spasms and narrowing of the airways. Asthmatics also produce more mucus and have less epithelium. This a thin tissue lining on the outer layer of the airway surface that acts as the first protective barrier between inhaled pathogens and the internal environment of the lung. This means there is less room for air to travel in the airways of asthmatics as they are narrower.
The combination of the flu and asthma symptoms is also highly problematic as the influenza virus directly target airway epithelial cells. And the flu infection also leads to more mucus secretion which can block the airway of asthmatics. This can lead to increased risk of complications and exposes the lungs to severe, possibly even long-term, damage.
Airways and asthma
Our recent research has also shown that healthy people have "mechanisms" in their airway epithelium to protect it from damage by the flu virus. But in asthmatics, these protective measures against infection are weaker so the influenza virus can cause more damage to airway epithelium.
For people with asthma then, it is highly recommended to take necessary precautions. Make sure you get the flu vaccination and follow good personal hygiene - such as covering coughs and sneezes and washing your hands regularly. And remember to repeat your flu vaccination every year because the protection from the vaccine decreases over time and the vaccine can change each year to cover the current virus strains.
And if you do end up with the flu as an asthmatic, don't panic, just make sure you see your doctor right away to check your symptoms and receive proper medications.
Author: Fatemeh Moheimani - Lecturer in Biomedical Science, Teesside University