Seven human cases of Guinea worm, and 709 infected dogs

**Dracunculiasis — Guinea worm disease — has gone from an estimated 3.5 million
cases in 1986 to 30 in 2017.** In **January–June 2018 there were seven human
cases**, in three countries: Angola, Chad and South Sudan.

That is one of the great public health achievements, achieved without a vaccine
or a drug — by filtering water, containing cases and educating communities.

And then:

Why the second number threatens the first

Eradication — as opposed to control — requires interrupting transmission
completely and permanently. That calculation assumed the parasite needed
people.

**The emergence of Guinea worm infections in dogs has complicated eradication
efforts**, and 709 against 7 is not a complication at the margin. The worm has
a reservoir that does not attend health education sessions, does not filter its
drinking water, and cannot be asked to keep a wound out of a pond.

A disease with an animal reservoir can be driven down and not driven out — the
same structural problem as toxigenic Corynebacterium ulcerans in pets, or
Trypanosoma cruzi in wildlife. Getting to zero in humans is no longer the
same as getting to zero.

The other obstacle

**Existence of infected dogs, especially in Chad, and impeded access because
of civil unrest and insecurity in Mali and South Sudan are now the greatest
challenges to interrupting transmission.**

The two remaining barriers are a dog and a war. Neither is a medical problem,
and the campaign has already solved every medical one.

Which is what the end of an eradication effort looks like: the last few cases
are in the hardest places to reach, and the method that took it from 3.5
million to seven does not obviously take it from seven to zero.

Source: Centers for Disease Control and Prevention, MMWR.