People with asthma who are admitted to hospital with pandemic influenza H1N1 (swine flu) are half as likely to die or require intensive care than those without asthma, according to new research.
The study, which is being presented at the European Respiratory Society's Annual Congress in Amsterdam, found that, despite asthma being among the commonest illnesses seen in patients admitted to hospital with H1N1, people with the condition had less severe outcomes.
In general, people with asthma are at risk of developing breathing difficulties when they have an infection, such as H1N1. When the lungs of people with asthma are infected with a virus, mucus and cells move into the narrow airways. This blocks the free movement of air.
The researchers studied 1,520 patients who were admitted to 75 hospitals in 55 cities and towns in the UK with the H1N1 virus. 480 (31%) of the people studied were aged under 16 yrs old. Asthma was the most common illness, affecting 385 (25%) of all patients.
The results showed that people with asthma and H1N1 more often had shortness of breath, more need for supplemental oxygen and greater severe respiratory distress than patients with H1N1 who did not have asthma. However, overall, people with asthma were half as likely to die or require high dependency or intensive care in hospital.
The link between asthma and less severe outcomes was seen even after the researchers took into account age, presence of other illnesses, and both antiviral and antibiotic use. What did seem to make a difference was that patients with asthma came to hospital earlier in the course of their H1N1 disease than other patients with flu. Also, those patients with asthma who had less severe outcomes were on regular inhaled steroids at the time of hospitalisation and received further steroids on admission.
Dr Malcolm Semple, from the University of Liverpool, said on behalf of the investigators: "Pandemic influenza can cause severe disease in people of all ages and those with asthma have a particularly high risk of needing hospital admission. Our results are the first to show that people with pandemic influenza and asthma for which they took regular inhaled steroids required less intensive treatment and had a better chance of recovering from H1N1. The prompt admission and appropriate hospital treatment of patients with asthma significantly improved their chance of recovery from pandemic influenza."
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