The 2001 anthrax attacks

1. Timeline of the anthrax letter attacks

One week after the September 11 attacks, anonymous letters containing deadly anthrax spores began arriving at media companies and congressional offices. Two waves of mailings were identified: the first on September 18, 2001, and the second on October 9, 2001, this time targeting two senators in addition to the media outlets already hit.

2. Clinical and public health toll

Between October 4 and November 20, 2001, 22 people developed the disease, split between 11 inhalational and 11 cutaneous cases. Five people died. The first victim, an employee at the editorial offices of a magazine that had received one of the letters, died on October 5 — the first death from anthrax in the United States in 25 years.

The other deaths included two employees of the Brentwood postal sorting facility, who were exposed to spores that leaked through the envelopes during mechanical mail processing. The remaining victims belonged to none of the identified risk groups and were almost certainly victims of cross-contamination through the general mail stream. Spores could indirectly contaminate other envelopes as they circulated through high-speed sorting machines, which aerosolized part of the contents of sealed envelopes. With the postal system having become an uncontrolled secondary vector of dissemination, 35 postal facilities and mailrooms were shut down.

With the postal system having become an uncontrolled secondary vector of dissemination, 35 postal facilities and mailrooms were shut down.

3. What is anthrax?

“Anthrax” is the name of the disease caused by the bacterium Bacillus anthracis. It’s an ancient disease, known since antiquity in livestock (cattle, sheep, goats) — a zoonosis long before it became a potential bioweapon.

When exposed to air and lacking nutrients, the anthrax bacillus produces spores — a dormant form of the bacterium — that are highly resistant, particularly to drying out and to many disinfectants. They can survive in soil for decades. Harmless on their own, spores become dangerous once they germinate inside a host and revert to an active bacterium, which then produces toxins that trigger a severe bacterial infection.

4. How anthrax spreads

Anthrax spores are transmitted mainly in three ways:

• Skin contact: historically the most common and least severe route
• Ingestion of contaminated meat: rare, but highly lethal
• Inhalation: the most dangerous route, spores in aerosol form reach the lung alveoli, then travel to the mediastinal lymph nodes, where they can germinate. The active bacterium multiplies, enters the bloodstream, and produces toxins on a massive scale. Early symptoms resemble the flu but rapidly progress to acute respiratory distress, pulmonary edema, and sepsis, which is often fatal without immediate treatment.

4.1. Inhalation, the cause of death in 2001

In the 2001 letter attacks, it was inhalational exposure that caused the deaths. Diagnosis was delayed because the early symptoms mimicked an ordinary flu. By the time the link to the letters was established, the therapeutic window had already closed for some patients. Once toxemia had taken hold, antibiotics effective against the bacterium could no longer neutralize the toxins already released into the body.

Following the investigation, US authorities concluded in 2010 that a single American microbiologist was responsible for the letters. He took his own life in 2008 after coming under suspicion. Reportedly struggling with psychological issues, he is believed to have carried out the attacks to demonstrate the need for the anthrax vaccine he had developed.

5. Public health and security aftermath

These events exposed the slowness of classical microbiological identification — 36 to 72 hours to identify a bacterium at the time — which had fatal consequences. They spurred faster development of real-time PCR screening tests for the bacterium.

In the United States, the BioWatch program was launched in the wake of the attacks to continuously monitor the air in major cities for biological agents.

In France, these events directly contributed to formalizing a biological CBRN doctrine: the Biotox plan, established in October 2001, includes a surveillance and alert component to detect an emerging epidemic as quickly as possible and to know how to respond to a suspected release, as well as a crisis-management component.

Since these contaminated letters were mailed in 2001, no act of bioterrorism has succeeded. Today, bioterrorism remains a credible, if unlikely, threat. Its potential for disruption or destruction nonetheless fully justifies preparing prevention measures and appropriate emergency response plans.