Severe H1N1 swine flu hits young and healthy

Death risk from H1n1 infection is 4 to 5 times higher among certain minority groups.

H1N1 infection gets more severe and dangerous in younger and otherwise healthier people, a stark contrast with seasonal influenza (flu), where around 90 per cent of fatal cases occur in people 65 years of age or older.

H1N1 pandemic affects fatally in age groups which are generally younger.To date, most severe H1N1 infections and deaths have occurred in adults under the age of 50 years.H1N1 deaths in the elderly comparatively rare. This is true for those most frequently infected, and especially so for those experiencing severe or fatal illness.

Severe respiratory failure, the most reported cause of death due to H1n1 pandemic infection are also in young and otherwise healthy people.In these patients, the virus directly infects the lung, causing severe respiratory failure. This is very peculiar to H1N1 pandemic and is rarely seen during seasonal influenza. Highly specialized and demanding care in intensive care units, usually with long and costly stays is often required to save these lives.

Several countries, during the winter season in the southern hemisphere, have viewed the need for intensive care as the greatest burden on health services. Some cities in these countries report that nearly 15 percent of hospitalized cases have required intensive care.

A higher risk of hospitalization and death is also found among certain subgroups, including minority groups and indigenous populations. The risk in these groups is four to five times higher than in the general population, studies show.

Possible explanations attributed include lower standards of living and poor overall health status, including a high prevalence of conditions such as asthma, diabetes and hypertension.

Certain medical conditions notably asthma, cardiovascular disease, diabetes and immunosuppression also increase the risk of severe and fatal illness. Worldwide, more than 230 million people suffer from asthma, and more than 220 million people are estimated to have diabetes.

An increased risk during pregnancy is now consistently well-documented across countries.This risk takes on added significance for a virus, like H1N1, that preferentially infects younger people.

Obesity is another condition leading to the fatality due to H1N1 infection.

Why the H1N1 strain becomes more aggressive with the young is not fully understood. Researchers, however, suggest that the H1 component, a subtype of the virus protein hemagglutinin, in both swine flu and human flu has a common ancestor.

H1 circulated in humans, evolving continuously during the 1918 and 1957 influenza pandemics. H1 then became inactive, replaced by other subtypes of hemagglutinin such as H3. H1 in humans reappeared in 1977 and has been a dominant subtype of human flu ever since.

Even though H1 has evolved significantly from 1977 to the present in humans, the H1 has evolved very little in pigs. Swine flu H1 has been very similar to the “original” 1918 and 1930 versions of H1.

So, it is assumed that most people born before 1957 were exposed to human H1 influenza. Their immune systems produced antibodies to Old H1. Since Old H1 has not been seen in humans in many years, younger people do not have antibodies to make them immune to old H1 which is very close to 2009 A/H1N1 swine flu.

Common symptoms for H1N1 flu have included fever, headache, upper respiratory tract symptoms (cough, sore throat, runny nose ), muscle aches, fatigue, vomiting and/or diarrhea.