global situation and disease burden for cholera€¦ · cholera and its control availability of...

Ad-hoc group of experts on cholera vaccines 28 October 2009

Global Situation and Disease Burden for Cholera

David A Sack, M.D. Professor, Dept of International Health,

Johns Hopkins and formerly the

Executive Director of ICDDR,B

Strategic Advisory Group of Experts on Immunization

28 October, 2009


Cholera is caused by intestinal infection with V cholerae O1 or O139

  Severe watery diarrhea leading to dehydration and shock within a few hours.

  Is adapted to water but is also capable of causing severe epidemics

  Healthy people can be dead in a few hours

  Massive fluid replacement may be needed for treatment


Cholera is caused by poverty, lack of sanitation and clean water

 Cholera as an issue of equity

–  Lack of clean water –  Lack of sanitation –  Lack of access to treatment

  Those most vulnerable can be provided with vaccines


PRESS RELEASE 14th October, 2009

  “Kenya’s Public Health Minister Beth Mugo has issued a new cholera alert and urged Kenyans to observe hygiene. The outbreak, which has affected parts of North Eastern, Eastern, Rift Valley and Nairobi provinces, has killed 48 people.” Photo from C.L. Chaignat


Cholera is changing…and getting worse (1)

Old Concepts New Findings Easily treated with rehydration therapy

• Case fatality rates exceed 4% in many areas due to lack of adequate treatment facilities, resources, and training

• Most cholera deaths occur in patients who do not reach treatment facility

Generally sensitive to antibiotics & Single dose is adequate

• Increasingly resistant to standard antibiotics

• Multiple doses of antibiotics are needed because of increasing MICs


Cholera is changing…and getting worse(2)

Old Concepts New Findings Worry of threat of serotype O139

• Threat of O139 remains – but not currently a public health problem

• Immediate threat is the new El Tor hybrid strains with classical toxin… associated with more severe disease

Africa has (unpredictable) outbreaks / Asia is endemic

• Both Africa and Asia have endemic cholera.

• Surveillance will assist in planning for cholera control.


Cholera is changing…and getting worse (3)

Old Concepts New Findings

Outbreaks have brief duration

• Recent outbreaks are prolonged – up to 9 months

Cholera control consists of improved water and sanitation and case management

• Control methods include water and sanitation and case management, but these are synergistically effective if combined with vaccines


Disease Burden of Cholera


Geographical distribution of cholera cases in Africa, 1995–2005

Cases of cholera or AWD are noted throughout sub-saharan Africa


Cholera in Asia


Example of Zimbabwe

22%

20% 14% 12%

93,482 cases Crude CFR 4.4%


Most Deaths Occur Among Patients Who Do Not Reach Health Facility

Cholera in Eastern DRC 2000-2007


0

500

1000

1500

2000

2500

3000

1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2

Jan Feb Mar Apr May Jun Jul Aug Sep

Estim

ated

num

ber o

f cas

es

Hospital Surveillance, Dhaka Hospital ICDDR,B January - September, 2009

VCO1 ETEC Rota


Aggregated distribution of reported cholera cases over 10 years in India, 1997-2006

• Most of the states reported cholera

• States without cholera were those that did not have any surveillance in place

• Potential to occur anywhere in India


Disease Burden of Cholera -Official and Unofficial Estimates-

  Reported to WHO (annually) –  About 250,000 cases –  2,000 to 6,000 deaths –  90%+ from Africa

  Usual numbers that are cited*. –  3 to 5 million cases –  120,000 deaths

* New Vaccine Development Establishing Priorities VOLUME II Diseases of Importance in Developing Countries . Part Two of a Two-Part Study by the Committee on Issues and Priorities for New Vaccine Development Division of Health Promotion and Disease Prevention and Division of International Health INSTITUTE OF MEDICINE, NATIONAL ACADEMIES PRESS. Washington, D.C.1986. www.nap.edu

Africa Asia Total # cases (x1000)

1,340 1,210 2,550

# deaths 160,000 50,000 210,000 More deaths estimated from Africa because of higher CFR and higher numbers who do not receive effective treatment

Burden based on recent estimates of incidence and case fatality rates for countries in Africa and Asia

Methods for estimates are available from David Sack, 2009


In Bangladesh, cholera is becoming more severe

  Proportion of cholera cases arriving at hospital in shock has been increasing

 Corresponds with the appearance of new El Tor / classical hybrid strains

  Similar clinical data is not available from Africa, but the strains are similar

Siddique AK, Nair GB, Alam M, Sack DA, et al. El Tor cholera with severe disease: a new threat to Asia and beyond. Epidemiol Infect. 2009 Aug 14:1-6


Epidemics / Endemic / Outbreaks

  Cholera is now endemic in many countries of Asia and Africa

–  Variable attack rates by season and year

–  El Tor cholera lives in surface and brackish water and can spread when there is breakdown in sanitation

  We often use the term “epidemic” or “outbreak” to explain a sudden increase in the number of cases

  From a practical sense, a country can be said to have endemic cholera if it has had documented cases during 3 or the last 5 years.

  Improved surveillance can help to refine rates of cholera as well as the seasons and groups of highest risk


Improved surveillance is needed to maximize impact of cholera vaccine

 Surveillance is needed to

•  help target those at highest risk by…

•  Age •  SES groups •  Geographic

•  help target season •  Focus messages about

cholera and its control

 Availability of vaccine will have other benefits for cholera control

•  May improve surveillance

•  Improve messages about cholera control

•  Help bring cholera “out of the shadows.”


Summary of key points (1) Issue Key points

Burden of disease • Burden of disease is much higher than is reflected among cases reported to WHO. • Case fatality rates about 4% in Africa • Most deaths occur in patients who do not reach treatment facility

Antibiotic resistance • Increasingly resistant to standard antibiotics

Severity of the illness • Disease appears to becoming more virulent with more patients arriving in shock, at least in Bangladesh

Endemic vs epidemic • Both Africa and Asia have endemic cholera


Summary of key points (2) Issue Key points

Duration of cholera “outbreaks”

• Recent outbreaks are prolonged and vaccines could reduce numbers of cases and deaths, if used promptly.

Relation to traditional methods of control

• Vaccines are synergistic with water and sanitation and will reduce the numbers of cases requiring treatment

Equity • Vaccines can be given to the poor and vulnerable…those who are less likely to receive treatment when ill

Availability of treatment

• “Treatment delayed is treatment denied.” Cholera kills in a matter of hours.

global situation and disease burden for cholera€¦ · cholera and its control availability of...

Documents