Severe acute respiratory syndrome (SARS) is a new threat to public health since November, 2002. The SARS is highly contagious and is believed to be transmitted by person-to-person through droplet and direct contact. The patients present with fever, chills, cough, myalgia, dyspnea, and diarrhea. The symptoms aggravate in the second week and nearly 40% of the patients develop respiratory failure that requires assisted ventilation. The mortality rate is reported as 6.5%-7%.

After several months, the world scientists found the etiology to be a new coronavirus not belonging to the previous coronavirus group I, II and III. The new virus is called SARS associated coronavirus (SARS-CoV).

Although the high morbidity and mortality of SARS occurred in adults, there was rare mortality reported in the children. The report from Hong Kong pointed out that the symptoms of SARS in younger children were milder and the clinical course was not as aggressive as in adults. Therefore, the aim of the project is to design the experiment to see the differences of immunological responses to SARS-CoV protein in healthy younger children, teenagers, and adults. The investigators hope that the result could explain the reason for milder disease in younger children and the immunological pathogenesis of SARS.

Inclusion Criteria:

• Healthy adults, children and cord blood