Some HS students were sickened in NYC, 1 person in Ohio...
But why do the officials fear a pandemic? Is this disease that contagious? Is it potentially that deadly?
Swine flu typically only passes from hogs to humans, but there are occasional outbreaks that go the human to human route. It's been seen before, but it's not the usual transmission route.
What makes this a potential pandemic virus is:
1) This is a new strain of swine flu that is a combination of human, hog, and bird virus, so our bodies haven't built up any immunities to it.
2) Those most at risk for serious cases are in the otherwise healthy adult category. Typically with flu those most at risk for death are infants, the elderly and those with weakened immune systems. But pandemic type influenzas fit this category of infecting otherwise healthy adults 25-40ish (SARS, 1918 influenza epidemic which killed 50 million worldwide).
3) This new strain is resistant to 2 of the 4 anti-virals (Tamiflu type drugs) on the market.
4) Viruses can mutate quickly.
5) There is no vaccine and even though plans are being made just in case, it will take months to get into production.
5) Widespread global travel--need I say more?
http://www.cdc.gov/swineflu/key_facts.htm
This is about avian flu but it explains the crossover between species well.
http://www.cdc.gov/flu/avian/gen-info/transmission.htm