  A/H1N1 epidemic data from Istanbul, Turkey during the period June
2009-February 2010 is analyzed with SEIR (Susceptible-Exposed-Infected-Removed)
model. The data consist of the daily adult hospitalization numbers and
fatalities recorded in various state hospitals serving an adult population of
about 1.5-2 million. June 2009-August 2009 period corresponds to the initial
stage of the epidemic where the hospitalization rate is nearly %100 and it is
excluded from further consideration. The analysis covers the September
2009-February 2010 period, the total number of hospitalizations and fatalities
being respectively 869 and 46. It is shown that the maximum correlation between
the number of fatalities and hospitalizations occur with a time shift of 9 days
and the proportionality constant is {\delta}=0.0537. The SEIR epidemic model is
applied to the data by back-shifting the number of fatalities. The
determination of the best fitting model is based on the L2 norms of errors
between the model and the data and the errors are around %10 and %2.6 for the
number of hospitalizations and fatalities, respectively. The parameters in the
model are I0, {\eta}, {\epsilon} and {\beta}, where I0 is the percentage of
people infected initially, {\eta} and {\epsilon} are related to the inverses of
the infection and incubation periods and {\beta}/{\eta} is the representative
of the basic reproduction number. These parameters are determined as
{\eta}=0.09 (1/{\eta} =11.11days), I0=10^-7.4, {\epsilon}=0.32 (1/{\epsilon}
=3.125 days), {\beta}=0.585, {\beta}/{\eta}=6.5.
