Almost 1 to 12 in us have asthma: study (AFP)

WASHINGTON- the United States asthma cases have increased by 12.3% since 2001, almost one in 12, or about US $ 25 million, are struck with chronic respiratory disease, the Government said Tuesday.

Additional cases of $ 4.3 million during the last decade also costs more for the US economy, 53 billion dollars for medical expenses and loss of productivity in 2001 to 56 billion in 2009, the Centers for Disease Control and Preventionsaid.

But officials say that they do not understand why more people get asthma, especially when Americans less smoke and the nation is taking steps to reduce air pollution.

"Despite the fact that the improvement of the quality of outdoor air, we have reduced both common asthma asthma triggers - secondhand smoke and smoking in General - is increasing," said Paul Garbe, head of Air Pollution and respiratory health of CDC branch.

"While we do not know the cause of the increase, our priority is gets people to better manage their symptoms."

Asthma can affect people of all ages, but tends to be more prevalent among the poor, said CDC report, vital signs, because the United States mark asthma awareness month.

African-American children have the highest rate of asthma, to 17.6%.

But all the ethnic and demographic groups have seen an increase in the incidence of asthma on 2001-2009 study period, which used data from the national survey on health interview and behavioural risk factors Surveillance System.

The overall prevalence of asthma in the population of the United States rose from 20.3 million people, in 2001 (7.3%), 24.6 million, in 2009 (7.3%).

Asthma can be triggered by "tobacco smoke, mold, pollution of outdoor air and infections related to influenza, cold - like symptoms and other viruses," said the CDC.

Most asthmatics can eliminate their symptoms if they are taking medications such as corticosteroids, and if they can "modify their environment to reduce or eliminate exposure to allergens and irritants", said the CDC.

Fresh medical were each year about $3,300 per person for the treatment of asthma, but among people without health insurance, two in five said that they could not afford medicines.