Mortality rates between seasonal influenza and Influenza A (H1N1-2009)

14 Sep 2009

Question No:  176  

Question

Name of the Person: Dr Lam Pin Min

To ask the Minister for Health (a) what are the mortality rates from seasonal influenza for the past three years as compared to the Influenza A (H1N1-2009); (b) what are the underlying cause(s) of death for both conditions; and (c) whether the mortality rates can be further reduced through appropriate medical prophylaxis.

Reply

Reply From MOH

1. Seasonal influenza as the direct cause for death is hard to establish.  Firstly, we do not routinely test patients for seasonal influenza.  Secondly, patients with complications often have other underlying medical conditions.  Their deaths may therefore be due to such underlying medical conditions, with seasonal influenza as a contributing factor.  Deaths due to seasonal influenza are therefore commonly estimated using mathematical modelling techniques. Using such methods, a local study published in 2006 estimated that there are about 600 influenza-related deaths in Singapore each year.  

2. As Influenza A(H1N1-2009) is a new strain and as the world is still in the midst of a pandemic caused by it, we carry out many more laboratory investigations on some of the infected patients, especially those who present with clinical complications.  Based on such observations, we have recorded 18 deaths due to this strain of influenza so far. As the methodologies for computing these death rates are different, we should not try to directly compare the death rates.

3. The underlying cause of death in influenza infection, whether by the seasonal influenza or the new strain, is commonly pneumonia. Influenza may also cause death by exacerbating pre-existing chronic heart disease resulting in a heart attack or chronic lung disease resulting in respiratory failure.  In the case of the new strain, there have also been complications and even deaths among some patients without any underlying medical conditions.  This continues to baffle the doctors and the scientists and we do not have good answers as yet.  While we are comforted by the fact that the new strain remains largely mild among the vast majority of infected patients, we cannot treat it lightly.  This is the reason why we remain in alert code yellow and not green.

4 To reduce mortality, the most important measure is vaccination.  When a safe and effective vaccine becomes available, we will make it widely available to the people. We will recommend it, especially to the front line staff, and to those at high-risk of developing serious complications from influenza.