The 2009 swine flu outbreak was caused by a strain of influenza virus that was believed to have undergone genetic mutation. While it contains genes similar to viruses that typically infect pigs, this particular strain was spreading among humans. Symptoms of swine flu included fever, sore throat, coughing, and general discomfort. A comparison of mortality rates for different influenza outbreaks showed that the 2009 swine flu strain had a mortality rate of 2.6% as of April 2009, which was higher than typical seasonal flu but lower than pandemics such as the 1918 Spanish flu or the avian flu.

2. The strain responsiblefor the 2009 swine flu outbreak is
believedto have undergone such a mutation
This virus is named Swine flu because one of
its surface proteins is similar to viruses that
usually infects pigs, but this strain is
spreadingin people and it is unknown if it
infectspigs.

4. • chills,
• fever,
• sore throat,
• muscle pains,
• severe headache,
• coughing,
• weaknessand
• general discomfort.

6. Epidemics
(avail. data)
Year Infected Deaths Mortality %
Death
rate/1,000
Spanish flu
(worldwide)
1918-19 1 billion 30 million 3% 30
Asian flu
(U.S.)
1957 45 million 70,000 .16% 1.6
Hong Kong
flu (U.S.)
1968-69 50 million 33,000 .07% .7
Avian flu
(worldwide)
1990-today 421 257 61% 610
SARS
(worldwide)
2002-03 8,096 774 9.6% 96
General flu
(U.S.)
yearly
average
50 million 36,000 .08% .8
Swine flu
(worldwide)
"confirmed"
as of
4/29/2009
273 153 2.6% 26