(CNN) Here's a look at the 2001 anthrax attacks, also referred to as Amerithrax.

Facts about anthrax

It can be contracted by handling products from infected animals or by breathing in anthrax spores and by eating undercooked meat from infected animals.

Anthrax has been blamed for several plagues over the ages that killed both humans and livestock. It emerged in World War I as a biological weapon.

The CDC categorizes anthrax as a Category A agent: one that poses the greatest possible threat for a negative impact on public health; one that may spread across a large area or need public awareness and requires planning to protect the public's health.

Amerithrax

Anthrax was sent via anonymous letters to news agencies in Florida and New York and a congressional office building in Washington.

Of the five victims who died of inhalation anthrax, two were postal workers. The other three victims were an elderly woman from rural Connecticut, a Manhattan hospital worker from the Bronx and an employee at a Florida tabloid magazine who may have contracted anthrax through cross-contamination.

No arrests have been made in the attacks.

4.8 million masks and 88 million gloves were purchased by the Postal Service for its employees, and 300 postal facilities were tested for anthrax.

Over 32,000 people took antibiotics after possible exposure to anthrax.

Victims

Stevens, Bob - photo editor at American Media Inc, dies of inhalation anthrax, October 5, 2001

Curseen, Joseph Jr. - DC area postal worker, dies of inhalation anthrax, October 22, 2001

Morris, Thomas Jr. - DC postal worker, dies of inhalation anthrax, October 21, 2001

Nguyen, Kathy - employee at Manhattan hospital, dies of inhalation anthrax, October 31, 2001

Lundgren, Ottilie - Connecticut woman, dies of inhalation anthrax, November 22, 2001

Timeline

October 5, 2001 - Sun photo editor Bob Stevens dies of inhalation anthrax.

October 12, 2001 - NBC News announces that an employee has contracted anthrax.

October 15, 2001 - A letter postmarked Trenton, New Jersey, opened by an employee of A letter postmarked Trenton, New Jersey, opened by an employee of Senate Majority Leader Tom Daschle contains white powdery substance later found to be "weapons grade" strain of anthrax spores. More than two dozen people in Daschle's office test positive for anthrax after the envelope is discovered.

October 19, 2001 - An unopened An unopened letter tainted with anthrax is found in the offices of the New York Post. One Post employee is confirmed to have a cutaneous infection and a second shows symptoms of the same infection.

October 21, 2001 - DC postal worker Thomas Morris Jr. dies of inhalation anthrax.

October 22, 2001 - DC postal worker Joseph Curseen dies of inhalation anthrax.

October 31, 2001 - Kathy Nguyen, a stockroom worker for the Manhattan Eye, Ear and Throat Hospital, dies of inhalation anthrax.

November 9, 2001 - The FBI releases a The FBI releases a behavioral profile of the suspect , who is probably a male loner and might work in a laboratory.

November 16, 2001 - A letter sent to Senator Patrick Leahy is found to contain anthrax. The letter is among those at the Capitol that has been quarantined. The letter contains at least 23,000 anthrax spores and is postmarked October 9, in Trenton, New Jersey.

November 22, 2001 - Ottilie Lundgren, a 94-year-old Connecticut woman, dies of inhalation anthrax.

January 2002 - FBI agents interview former US Army bioweapons scientist Steven Hatfill as part of the anthrax investigation.

June 2002 - Bioweapons researcher Hatfill is named a "person of interest" by the FBI.

June 25, 2002 - The FBI searches Hatfill's Maryland apartment and Florida storage locker with his consent.

June 27, 2002 - The FBI says it is focusing on 30 biological weapons experts in its probe.

August 1, 2002 - The FBI uses a criminal search warrant to search Hatfill's Maryland apartment and Florida storage locker a second time; anthrax swab tests come back negative.

August 6, 2002 - Attorney General John Ashcroft refers to Hatfill as a "person of interest."

August 11, 2002 - Hatfill holds a press conference declaring his innocence. He holds a second one on August 25, 2002.

September 11, 2002 - The FBI searches Hatfill's former apartment in Maryland for the third time.

August 26, 2003 - Hatfill files a civil lawsuit against Attorney General John Ashcroft, the Justice Department and the FBI claiming his constitutional rights have been violated. The suit alleges violations of Hatfill's Fifth Amendment rights by preventing him from earning a living, violations of his Fifth Amendment rights by retaliating against him after he sought to have his name cleared in the anthrax probe and the disclosure of information from his FBI file. The suit also seeks an undetermined amount of monetary damages.

July 11, 2004 - The former headquarters of American Media, Inc. in Boca Raton, Florida, where Bob Stevens contracted the anthrax is pumped full of chlorine dioxide gas for decontamination. This was the last building exposed to anthrax in the fall of 2001.

June 27, 2008 - The The Justice Department reaches a settlement with Hatfill . The settlement requires the Justice Department to pay Hatfill a one-time payment of $2.825 million and to buy a $3 million annuity that will pay Hatfill $150,000 a year for 20 years. In return, Hatfill drops his lawsuit, and the government admits no wrongdoing.

July 29, 2008 - Bruce Ivins, a former researcher at the Army's bioweapons laboratory at Fort Detrick, Maryland, dies after overdosing during a suicide attempt on July 27.

August 8, 2008 - The Justice Department formally exonerates Hatfill.

September 25, 2008 - Court releases more documents including e-mails that Ivins sent to himself.

February 19, 2010 - The Justice Department, FBI and US Postal Inspection Service announce its investigation into the The Justice Department, FBI and US Postal Inspection Service announce its investigation into the 2001 anthrax mailings is at an end

March 23, 2011 - A report, entitled A report, entitled The Amerithrax Case , is released through the Research Strategies Network, a non-profit think tank based in Virginia. According to the report, old mental health records suggest Ivins should have been prevented from holding a job at a US Army research facility in Maryland. The report was requested by the US Department of Justice.

October 9, 2011 - New York Times reports indicate there are scientists questioning the FBI assertions regarding Ivins. Possibly Ivins, if he was involved, worked with a partner. Also, the scientists say the presence of tin in the dried anthrax warrants that the investigation be reopened.