Cholera is an acute life-threatening
disease characterized by enormous loss of fluid and electrolytes
due to profuse diarrhea and vomiting. This waterborne disease has
been responsible for global scourges for centuries; it is often
seen in the wake of disaster situations, both man-made and natural.
Descriptions resembling cholera exist in ancient Sanskrit literature
(500 BC to 400 BC) from India.1 Until
the early 19th century, this disease was primarily confined to the
Indian subcontinent, especially the Ganges delta region. The first
pandemic of cholera in 1817–1823 began with spread of disease
outside the Indian subcontinent along trade routes to the west as
far as southern Russia. The second pandemic started in 1826 and
it reached the major European cities by the early 1830s and the
eastern United States in 1832. This pandemic continued for 19 years.
John Snow, a prominent London physician, observed a correlation
between the disease and the source of public water, leading to the
control of the epidemic by removing the handle of the Broad Street
water pump. During the third pandemic (1852–1859), Filippo
Pacini described the curved bacilli from the intestinal contents
of cholera patients and named them Vibrio cholerae.1,2 Later,
Robert Koch proved that the curved bacillus was the cause of cholera.
The seventh pandemic, which began in 1961, is the most well studied.3 Unlike
the previous pandemics, which were caused by classical V cholerae O1
biotype; the V cholerae O1El Tor biotype, which
first appeared in Indonesia in 1937, caused the seventh pandemic.
This strain began to spread to India in 1964, Middle East in 1965,
Africa and southern Europe in 1970, and South America in 1991. This
pandemic led to the use of oral rehydration solution (ORS) to treat
cholera. Early during this pandemic, mortality rates were approximately 50% in
Africa. Later, with rapid response time and effective treatment,
less than 1% mortality rate was observed in Peru.4 Until
1992, only V cholerae O1 serogroup caused epidemic
cholera. Some other serogroups could cause sporadic cases, but not
epidemic cholera. However, the most recent outbreak of cholera in
1992 in Chennai (formerly Madras), India, was caused by a new V
cholerae serogroup, designated O139 or Bengal strain. This
strain rapidly spread from India to Bangladesh and later to other
11 countries in Asia. If this strain continues to spread throughout
the world, then it would be the eighth cholera pandemic.1,5,6 The
outbreaks caused by V cholerae O139 have spread
rapidly even among the elderly who were previously exposed to cholera caused
by V cholerae O1, suggesting that the immunity
to V cholerae O1, whether from natural infection
or vaccination, is not protective against V cholerae O139.
Serogroups O139 and O1 now coexist and continue to cause large outbreaks
of cholera in the Indian subcontinent.
Endemic cholera caused by V cholerae O1 primarily
affects children. For instance, in Bangladesh the infection was