Cholera epidemiology and demographics

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editors-In-Chief: Sara Mehrsefat, M.D. [2], Tarek Nafee, M.D. [3], Priyamvada Singh, MBBS [4]

Overview

In 2015, 172,454 cases and 1,304 deaths of cholera were reported to WHO worldwide. Outbreaks continued to affect several countries. Overall, 41% of cases were reported from Africa, 37% from Asia, and 21% from the Americas. In the early 1980s, mortality rates are believed to exceeded 3 million deaths a year. It is difficult to calculate exact numbers of cases, as many go unreported due to concerns that an outbreak may have a negative impact on the tourism of a country. Cholera remains both epidemic and endemic in many areas of the world. Although much is known about the mechanisms behind the spread of cholera, this has not led to a full understanding of what makes cholera outbreaks happen some places but not others. Lack of adequate treatment of human feces and/or drinking water greatly facilitates the spread of cholera. Bodies of water can serve as a reservoir of the disease. Seafood shipped over long distances can also spread the disease. Cases of cholera were not observed in the Americas for most of the 20th century, thought the disease reappeared towards the end of that century and seems likely to persist.

2017 Yemen outbreak

• Since the outbreak started in April 27, 2017, a total of 101,820 cases  were suspected from which 791 died.
• Most of the fatalities are children below 15 years (46% of cases) and elderly over 60 years (33% of cases).
• The disease is spreading in 19 out of 23 governorates in the country that is war torn.
• The health system in the country is nearly destroyed which makes the mission to control the disease even harder. After 2 years of conflict, less than half of the healthcare centers are working. Medical supplies are entering Yemen in a rate that is third of what it used to be before the conflict. Moreover, infrastructure is terribly damaged preventing 14.5 million people from having access to clean water and sanitation.
• Efforts by WHO and UNICEF are made to control the outbreak especially in the “hotspots” or the most affected areas.
• 66.7 million US dollars are invested in the fight against the outbreak. Till the moment, 3.5 million people have been reached through disinfecting water tanks, chlorination of water and distributing hygiene kits.

{{fontcolor|#FFF|Date		Deaths	{{fontcolor|#FFF| More details
June 11th, 2017	101,820	791	Since the outbreak started in April 27, 2017, a total of 101,820 cases  were suspected from which 791 died. Most of the fatalities are children below 15 years (46% of cases) and elderly over 60 years (33% of cases). The disease is spreading in 19 out of 23 governorates in the country that is war torn. The health system in the country is nearly destroyed which makes the mission to control the disease even harder. After 2 years of conflict, less than half of the healthcare centers are working. Medical supplies are entering Yemen in a rate that is third of what it used to be before the conflict. Moreover, infrastructure is terribly damaged preventing 14.5 million people from having access to clean water and sanitation. Efforts by WHO and UNICEF are made to control the outbreak especially in the “hotspots” or the most affected areas. 66.7 million US dollars are invested in the fight against the outbreak. Till the moment, 3.5 million people have been reached through disinfecting water tanks, chlorination of water and distributing hygiene kits.
June 25th, 2017	200,000	1300	Number of suspected cases has doubled so as the number of dead, making it the worst cholera outbreak in the recent history. Numbers are expected to rise in the next few weeks. WHO and UNICEF are scaling up their efforts to contain the outbreak. Rapid response teams are going from house to house educating people about the effective measures for primary and secondary prevention. Local health workers (estimated 30,000 of them) have not been paid for 10 months due to the ongoing conflict and economic crisis, making the efforts to contain the infection more difficult.

Country	Date	Cases (confirmed and suspected)	Deaths	More details
The Democratic Republic of Congo (DRC)	May 12th, 2017	9	1 (11.1%)	In May 12, 2017, WHO declared a lab confirmed case in Bas-Uele region in the northeast Congo. Nine cases were hospitalized for hemorrhagic fever and three of them died. Only one case was confirmed to have Ebola virus. Despite being a serious situation, it's considered a good sign that the outbreak struck in a remote and forested region
	May 14th, 2017	11	3 (27%)	The extent of the outbreak is not yet fully estimated but WHO recommends restriction of trade and travel with DRC. WHO's general director in Africa has met governmental representatives in Kinshasa to discuss measures to contain the outbreak.
	May 17th, 2017	11	3 (27%)	About 125 people of the contacts of the infected people are being monitored for possible development of the symptoms. Isolation facilities are being set up in case the outbreak involves wider areas.
	May 18th, 2017	18	3 (17%)	The number of contacts of infected people that are being followed and monitored for development of symptoms rises to 400. Personal Protective Equipment (PPE) for healthcare workers has been shipped to DR Congo. UNICEF workers have arrived and began aiding in setting up mobile laboratory sites in nearby regions. The Congolese government is in talks with the WHO in regards to "ring vaccination" of patient contacts with an experimental vaccine developed by an American company.
	May 19th, 2017	29	3 (10%)	416 contacts of infected patients are being followed.
	May 21st, 2017	32	4 (13%)	The reported cases are from five health areas: Nambwa, Muma, Ngayi, Azande, and Ngabatala
	May 22nd, 2017	34	4 (12%)	54 contacts completed daily contact monitoring and 362 remain under follow up with daily monitoring
	May 22nd, 2017	37	4 (11%)	Institut National de Recherche Biomedicale (INRB)) mobile laboratory began processing samples with 22 testing negative by PCR
	May 22nd, 2017	38	4 (11%)	33 samples have tested negative by PCR thus far 3 additional contacts were identified. 365 contacts remain under daily follow up for signs and symptoms of Ebola.
	May 25th, 2017	43	4 (9%)	Experts estimate  that the 1400 Km isolation around Kinshasa has limited the spread of the disease. However, refugee flow across the borders towards the afflicted Bas-Uele region escaping the recent attacks of fighting militias puts the refugees at increased risk of infection and undermines the efforts to contain the outbreak.
	May 28th, 2017	43	4 (9%)	No new reported cases nor deaths 357 contacts are being monitored for symptoms and signs of ebola Based on the limited number of new confirmed cases, the risk is declared to be low with simulated scenarios predict no further cases in the following 30 days.
	May 30th, 2017	52	4 (7%)	Authorities in DRC approves the new  rVSV-ZEBOV vaccine.
	June 3rd, 2017	52	4 (7%)	No new confirmed cases .. with the last confirmed case was on May 11th 2017 All the contacts of confirmed cases completed the follow up period of 21 days and none of them developed the symptoms of Ebola. The risk remains low but not negligible.

Epidemiology and Demographics

Incidence

• In 2015, 172,454 cases and 1,304 deaths of cholera were reported to WHO worldwide. Outbreaks continued to affect several countries.
• Overall, 41% of cases were reported from Africa, 37% from Asia, and 21% from the Americas.
• Worldwide, cholera affects an estimated 1.4 to 4.3 million people and causes 28,000 to 142,000 deaths a year as of 2012.

Origin and Spread

Cholera was originally endemic to the Indian subcontinent, with the Ganges River likely serving as a contamination reservoir. It spread by trade routes (both land- and sea-based) to Russia, then to Western Europe, and from Europe to North America. Cholera is no longer considered an issue in Europe and North America, due to filtering and chlorination of the water supply.

Gender

Cholera occurs equally in males and females.

Age

• In non-endemic areas, cholera occurs equally in all age groups.
• In endemic regions, children older than the age of 2 years are most commonly infected which cholera. Illness is uncommon before children reach 2 years of age, likely due to passive immunity.

Geographic Distribution

Cholera in the United States

In the United States, the occurrence of cholera is very low (0-5 cases per year) and is usually due to ingestion of contaminated food or infection during international travel. There has been a modest increase in imported cases since 1991 related to travel and ongoing epidemics.

Cholera in the Developing World

The highest incidencce of cholera in the developing world occurs in the following regions:

• Africa: Mozambique, Liberia, Democratic Republic of Congo, Niger
• Asia: Indonesia, Bangladesh, India
• The Americas: Dominican Republic, Haiti
• The Middle East: Yemen

Case Fatality Rates

• In 2015, the case fatality rates (CFRs) for cholera ranged from 0.0% to 11.7%; globally, the overall CFR was 0.8%.
• CFRs >1% were reported by 15 countries.
  • Of these 15 countries, CFR >5% were reported in Myanmar and Niger.
  • In Yemen, the case-fatality rate is reported to be between 4% to 5%.
• The average case fatality rate for Europe and the Americas is estimated to be around 1%.
• At the Treatment Center of the International Center for Diarrheal Disease Research in Bangladesh, less than 1% of patients with severe dehydration die.
• In Africa, a marked decline in case fatality rates has reported since 1970.
• in South America, low case fatality rates have been achieved.