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MINSTRY OF HEALTH HOMS DIRECTORATE OF HEALTH Cholera epidemiology

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Title: MINSTRY OF HEALTH HOMS DIRECTORATE OF HEALTH Cholera epidemiology


1
MINSTRY OF HEALTH HOMS DIRECTORATE OF HEALTH
Cholera epidemiology
  • Dr. Hisham Aldabbagh

2
  • Cholera is still a subject of intense interest
    for modern-day epidemiology
  • in the 1800s a causal link between cholera
    transmission and exposure to contaminated water
    was established
  • More recently, researchers have begun to
    understand more about the mechanisms of
    infectiousness of the cholera pathogen Vibrio
    cholerae

3
  • Cholera has been very rare in industrialized
    nations for the last 100 years however, the
    disease is still common today in other parts of
    the world, including the Indian subcontinent and
    sub-Saharan Africa
  • Cholera is an acute, diarrheal illness caused by
    infection with the bacterium Vibrio cholerae. it
    is often mild or without symptoms, but sometimes
    it can be severe. Approximately one in 20
    infected persons has severe disease characterized
    by profuse watery diarrhea, vomiting, and leg
    cramps. In these persons, rapid loss of body
    fluids leads to dehydration and shock. Without
    treatment, death can occur within hours.

4
  • A person may get cholera by drinking water or
    eating food contaminated with the cholera
    bacterium. In an epidemic, the source of the
    contamination is usually the feces of an infected
    person. The disease can spread rapidly in areas
    with inadequate treatment of sewage and drinking
    water.
  • The cholera bacterium may also live in the
    environment in brackish rivers and coastal
    waters. Shellfish eaten raw have been a source of
    cholera, The disease is not likely to spread
    directly from one person to another therefore,
    casual contact with an infected person is not a
    risk for becoming ill.

5
  • Vibrio cholerae is a Gram-negative bacterium that
    produces cholera toxin, an enterotoxin, whose
    action on the mucosal epithelium lining of the
    small intestine is responsible for the disease's
    infamous characteristic, exhaustive diarrhea
  • The major reservoir for cholera was long assumed
    to be humans themselves, but considerable
    evidence exists that aquatic environments can
    serve as reservoirs of the bacteria

6
  • In endemic regions, such as South Asia, cholera
    is seasonal, with explosive outbreaks occurring
    once or twice a year, depending on the region.
    Periodically, pandemic waves of cholera roll
    across the world causing a heavy death toll.

7
  • 1816-1826 - First cholera pandemic began in
    Bengal, and then spread across India by 1820.
    Then extended as far as China and the Caspian Sea
  • 1829-1851 - Second cholera pandemic reached
    Europe, London and Paris in 1832. In London, the
    disease claimed 6,536 victims in Paris, 20,000
    succumbed (out of a population of 650,000) with
    about 100,000 deaths in all of FranceThe epidemic
    reached Russia , Quebec, Ontario and New York in
    the same year and the Pacific coast of North
    America by 1834.

8
  • 1849 - Second major outbreak in Paris. In London,
    it was the worst outbreak in the city's history,
    claiming 14,137 lives, over twice as many as the
    1832 outbreak. In 1849 cholera claimed 5,308
    lives in the port city of Liverpool, England, and
    1,834 in Hull, England.An outbreak in North
    America took the life of former U.S. President
    James K. Polk. Cholera spread throughout the
    Mississippi river system killing over 4,500 in
    St. Louis and over 3,000 in New Orleans as well
    as thousands in New York In 1849 cholera was
    spread along the California and Oregon trail as
    hundreds died on their way to the California Gold
    Rush, Utah and Oregon.

9
  • 1852-1860 - Third cholera pandemic mainly
    affected Russia, with over a million deaths. In
    1853-4, London's epidemic claimed 10,738 lives.
  • 1854 - Outbreak of cholera in Chicago took the
    lives of 5.5 of the population (about 3,500
    people).
  • 1863-1875 - Fourth cholera pandemic spread mostly
    in Europe and Africa

10
  • 1866 - Outbreak in North America. In London, a
    localized epidemic in the East End claimed 5,596
    lives. Also a minor outbreak at Ystalyfera in
    South Wales. Caused by the local water works
    using contaminated canal water, it was mainly its
    workers and their families who suffered, 119
    died. In the same year more than 21,000 people
    died in Amsterdam, The Netherlands

11
  • 1881-1896 - Fifth cholera pandemic The 1892
    outbreak in Hamburg, Germany killed 8,600 people.
    This was the last serious European cholera
    outbreak.
  • 1899-1923 - Sixth cholera pandemic had little
    effect in Europe because of advances in public
    health, but major Russian cities and the Ottoman
    Empire were particularly hard hit by cholera
    deaths.

12
  • 1961-1970s - Seventh cholera pandemic began in
    Indonesia, called El Tor, and reached Bangladesh
    in 1963, India in 1964, and the USSR in 1966.
    From North Africa it spread into Italy by 1973.
    In the late 1970s, there were small outbreaks in
    Japan and in the South Pacific. There were also
    many reports of a cholera outbreak near Baku in
    1972

13
  • January 1991 to September 1994 - Outbreak in
    South America. Beginning in Peru there were 1.04
    million identified cases and almost 10,000
    deaths.
  • In 1992 a new strain appeared in Asia,
    nonagglutinable vibrio (NAG) named O139 Bengal.
    It was first identified in Tamil Nadu, India and
    for a while displaced El Tor in southern Asia
    before decreasing in prevalence from 1995 to
    around 10 of all cases. It is considered to be
    an intermediate between El Tor and the classic
    strain and occurs in a new serogroup.

14
  • Iraq outbreaks
  • - 2oo7 15000 cases
  • - 2008 700 cases

15
  • November 2008 - Doctors Without Borders reported
    an outbreak in a refugee camp in Congo's eastern
    provincial capital of Goma. Some 45 cases were
    reportedly treated between November 7th through
    9th.

16
  • November 2008 - More than an estimated 11,000
    people in Zimbabwe are believed to be infected
    with more than 970 recorded deaths observed
    during a current and ongoing outbreak. The number
    of people infected is believed to be
    significantly higher. The outbreak is a result of
    mismanagement of water purification
    infrastructure. Subsequent outbreaks are being
    observed in neighbouring countries as the medical
    infrastructure in Zimbabwe is severely crippled
    by hyperinflation leading to several Zimbabwean
    citizens seeking medical care elsewhere.

17
  • Until the 1970s, V. cholerae was thought to be a
    human-specialized parasite, incapable of
    persisting outside its host. But in the 1990s, it
    became clear that V. cholerae was a successful
    member of the brackish water microbial community,
    living in association with plankton in an
    unculturable but viable state

18
  • Volunteer studies suggest that cholera infection
    requires consumption of a heavy infectious dose,
    which is unlikely to be found in the environment
    in the beginning of the epidemic season, even
    considering the blooming of aquatic V. cholerae..

19
Susceptibility
  • Recent epidemiologic research suggests that an
    individual's susceptibility to cholera (and other
    diarrheal infections) is affected by their blood
    type Those with type O blood are the most
    susceptible while those with type AB are the most
    resistant. Between these two extremes are the A
    and B blood types, with type A being more
    resistant than type B

20
  • About one million V. cholerae bacteria must
    typically be ingested to cause cholera in
    normally healthy adults, although increased
    susceptibility may be observed in those with a
    weakened immune system, individuals with
    decreased gastric acidity (as from the use of
    antacids), or those who are malnourished

21
The Hyperinfectious State
  • The passage of V. cholerae through the human gut
    would promote the expression of genes that would
    make the bacteria more infective, that is, more
    capable of surviving and growing in the
    intestinal environment
  • This hyperinfectious state would be lost after
    a few hours outside the gutthat is, after being
    outside the gut for more than 18 hours
  • The infectious dose is 700 times smaller if
    consumed water contains HI bacteria. Infected
    persons shed HI bacteria into their feces, which
    decay to the non-HI state in an average of 18
    hours

22
  • Explosive outbreaks depend on the number of cases
    produced by contact with recently shed bacteria(
    HI bacteria )
  • This would be the case in a community where poor
    basic hygienic conditions make contact with
    recently shed bacteria a probable event.

23
  • Any public health action to reduce direct
    transmission will have a large impact on the rate
    of disease spread. In other words, any measure
    that delays fecaloral transmission, even the
    simple act of washing hands before a meal, would
    have a stronger than previously expected impact
    on cholera transmission
  • Thus, public health strategies based on
    increasing hygiene standards would be effective ,
    even if more permanent improvements, such as
    proper sewage treatment, were impossible

24
How long will the cholera epidemic last?
  • Predicting how long a cholera epidemic will last
     is difficult. The cholera epidemic in Africa has
    lasted more than 30 years. In areas with
    inadequate sanitation, a cholera epidemic cannot
    be stopped immediately.
  •  There are no signs that the global cholera
    pandemic will end soon.
  • Major improvements in sewage and water treatment
    systems are needed in many countries to prevent
    future epidemic cholera

25
Distribution of cholera
26
Is a vaccine available to prevent cholera?
  • A recently developed oral vaccine for cholera is
    licensed and available in some countries (Dukoral
    from SBL Vaccines). The vaccine appears to
    provide somewhat better immunity and have fewer
    adverse effects than the previously available
    vaccine. However, CDC does not recommend cholera
    vaccines for most travelers, nor is the vaccine
    available in the United States .

27
  • Sensitive surveilence and prompt reporting allow
    for containing cholera epidemics rapidly. Cholera
    exists as a seasonal disease in many endemic
    countries, occurring annually mostly during rainy
    seasons. Surveillance systems can provide early
    alerts to outbreaks, therefore leading to
    coordinated response and assist in preparation of
    preparedness plans.

28
  • Efficient surveillance systems can also improve
    the risk assessment for potential cholera
    outbreaks. Understanding the seasonality and
    location of outbreaks provide guidance for
    improving cholera control activities for the most
    vulnerable. This will also aid in the developing
    indicators for appropriate use of oral cholera
    vaccine.

29
  • Thanks for your concern
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