Cate Vojdik
AC360° Writer

The swine flu crisis is erupting on a milestone week for President Obama; today is 100th day of his presidency.

Arbitrary or not, Day 100 has become part of the drill when it comes to covering new administrations – and tonight, CNN will have extensive coverage, starting with President Obama’s prime-time press conference at 8 p.m. eastern. We’ll cover the presser live and follow with plenty of analysis and reality-checking. We’ll also give you a chance to grade the president - and Congress - on their performance so far.

Starting at 11 p.m. eastern, 360 will have the latest on the swine flu outbreak, which health officials say is hurtling toward a pandemic.

Today brought a flood of new developments in this fast-moving story. The World Health Organization raised its alert another notch, from 4 to 5 – its second-highest level. More than 140 cases have been confirmed in at least 9 countries. Germany and Austria are the latest to report swine flu.

In the U.S., the number of confirmed cases grew to 91. The virus has been reported in at least 10 states, and hundreds of suspected cases are being investigated. A toddler in Texas became the first U.S. fatality. He was visiting from Mexico and died in a Houston hospital.

Health officials say we can expect more deaths. The new Health and Human Services Secretary, Kathleen Sebelius, held a news conference today, her first full day on the job. Talk about being thrown into the fire.

A lot of viewers have been asking why we’re devoting so much coverage to the swine flu story. They point out, rightly, that the death toll hasn’t yet come close to the average annual death toll from the common flu, which kills around 36,000 Americans each year. But that’s just one piece of the story and one measurement of the danger.

A couple of factors make this flu virus especially newsworthy – and potentially very dangerous. Health officials are battling a brand-new strain of flu, which means they have to create a new vaccine for it. That could take months. Think of it this way: Until a vaccine is developed the virus is free to operate under the radar. Our immune systems haven’t seen anything like it before, leaving our bodies vulnerable to invasion. Imagine the virus speeding down a highway at 100 mph with no police cars to chase it.

While it’s true more people have died this year from the common flu, health experts say a novel flu strain, like the swine flu we’re seeing, has the potential to kill even more people than the common flu. There’s no way to know if it will. But public health responses are premised on potential risks. Because this virus appears to be spreading easily from person to person, and because genetically it’s an unknown enemy, it’s potentially a more dangerous threat than the flu that’s been knocking people flat all season.

We’ll have all the latest on the outbreak, starting at 11 eastern. 360 M.D. Sanjay Gupta and Dr. Carlos del Rio will be answering your questions again tonight. They’ll also help us bust some myths about the flu. Dr. del Rio is a professor of global health at Emory University’s Rollins School of Public Health. He’s also a native of Mexico and has been working with Mexico’s government since the swine flu outbreak began.

You can post your questions during the live chat on AC360.com during the show. You can also send it to facebook.com/andersoncooper360 or via a tweet to @andersoncooper.

See you at 11 p.m. eastern.