[7] As of November 2021, there have been more than 2.5 million cases reported, and more than 4,000 people have died in the Yemen cholera outbreak, which the United Nations deemed the worst humanitarian crisis in the world at that time.

[8][9] However, the outbreak has substantially decreased by 2021, with a successful vaccination program implemented and only 5,676 suspected cases with two deaths reported between January 1 and March 6 of 2021.

[8] The cholera outbreak was worsened as a result of the ongoing civil war and the Saudi Arabian-led intervention in Yemen against the Houthi movement that began in March 2015.

[6] The UNICEF and World Health Organization (WHO) executive directors stated: "This deadly cholera outbreak is the direct consequence of two years of heavy conflict.

An estimated 30,000 dedicated local health workers who play the largest role in ending this outbreak have not been paid their salaries for nearly ten months.

[26] By the end of October, cases had been reported in the governorates of Al-Bayda, Aden, Al-Hudaydah, Hajjah, Ibb, Lahij and Taiz and,[27] by late November, also in Al-Dhale'a and Amran.

[13] UNICEF and the WHO attributed the outbreak to malnutrition, collapsing sanitation and clean water systems due to the country's ongoing conflict, and the approximately 30,000 local health care workers who had not been paid for almost a year.

[14] These factors resulted in a delayed vaccination program, which was not started until more than one million people were already ill.[8] Even before civil war affected Yemen, it was "beset by circumstances that made it ripe for cholera".

[41] Because of the ongoing conflict in Yemen, and resulting displacement of people who do not have adequate food, waster, housing or sanitation, pre-existing conditions were exacerbated.

[11] Doctors Without Borders reported that a Saudi Arabian coalition airstrike hit a new Médecins Sans Frontières cholera treatment center in Abs, in northwestern Yemen.

[42] Grant Pritchard, Save the Children's interim country director for Yemen, stated in April 2017, "With the right medicines, these [diseases] are all completely treatable – but the Saudi Arabia-led coalition is stopping them from getting in.

"[43] Yemen's wastewater and solid waste management systems are the least developed among Middle Eastern countries, which has been a major contributor to the cholera outbreak.

[47][48] High concentrations of Escherichia coli, Streptococcus faecalis, Klebsiella pneumoniae, Enterobacter aerogenes, Salmonella  typhi, S. typhimurium, and Shigella sonnei - among other harmful fecal coliforms - are present in this wastewater, and transmit to humans when they consume foods irrigated by it.

[45] The El Niño–Southern Oscillation phenomenon is a major driver of climate variability associated with health outcomes, including influencing cholera dynamics due to changes in rainfall.

[50] Based on this evidence, it is hypothesized that the El Nino conditions over the Gulf of Aden may have contributed to the transmission of cholera from the Horn of Africa to Yemen through wind effects on cholera-contaminated flying insects.

[13] Qadri, Islam and Clemens write that the dramatic April 2017 resurgence coincided with heavy rains, and "was amplified by war-related destruction of municipal water and sewage systems".

[6] An International Committee of the Red Cross (ICRC) worker in Yemen noted that April's cholera resurgence began ten days after Sana'a's sewer system stopped working.

[53] The geography of Yemen means that the Western mountainous plateau sees more rainfall, and has therefore an increased risk of high cholera incidence due to water precipitations.

[56] The COVID-19 pandemic has further burdened the already overwhelmed healthcare system in Yemen fighting a number of diseases including cholera, dengue fever, and malaria.

[8] In the management of cholera, they stated that they trained 900 health workers and ran 139 oral rehydration locations, to treat 700,000 reported cases of the illness.

[8] UNICEF reported that they ran awareness campaigns with 20,000 promoters, provided water to more than one million individuals, served as the WaSH lead, and delivered "40 tons of medical equipment including medicine, oral rehydration solution, IV fluids and diarrhea kits".

[8] As of June 2, 2020, Canada has pledged $40 million in humanitarian aid for Yemen to help the politically unstable country cope with cholera, malaria, dengue fever, and diphtheria along with COVID-19.

[62] On 23 June 2017, Saudi Arabia's crown prince, Mohammed bin Salman, authorized a donation in excess of $66 million for cholera relief in Yemen.

[66] The U.S. is also planning to provide $55 million in economic and development assistance, including programs to support livelihoods, rebuild infrastructure, and restore access to education.

[66] On March 27, 2020, the Trump administration cut $70 million in assistance destined for northern Yemen, framing the decreased funding as a response to the interference of Houthi rebels.

[68] The UK has partnered with organizations including UNICEF and the International Organisation for Migration (IOM) to combat the cholera disease in Yemen.

[68] The UK's humanitarian response includes nutrition support, clean water, sanitation, and medical supplies, such as chlorine tablets and hygiene kits.

[68] The UK Department for International Development (DFID) has also worked with the Met Office, NASA and U.S. scientists to deploy a model to predict and effectively respond to outbreaks of cholera.

[69] DFID Secretary Priti Patel has urged the international community to follow the UK government's steps to curb the cholera outbreak.