Apart from infectious bloodborne diseases, reactions associated with toxic and semi-toxic additives, unknown purity levels, and the possibility of overdose, intravenous drug users also have to weigh the possibility of fatal bacterial infections.

In April of 2000, a contaminated batch of heroin began a deadly march across Great Britain. By August, more than 40 people in England, Wales, Scotland, and Ireland died. Researchers eventually identified Clostridium vovyi type A, a highly toxic bacterium that grows in soil and animals. Clostridium itself is harmless, but its dormant spores produce deadly toxins when released.

Health officials said that bacterial infections are rather common in people who ingest drugs intravenously, but such deadly outbreaks are unusual.

Apparently all those who died had injected the drug intramuscularly rather than directly into the bloodstream. Oxygen in the blood usually kills any stray bacterium in the heroin, but there is no oxygen...