As the war entered its Fifth year, Yemen’s humanitarian needs increased tremendously, with 22.2 million Yemenis – nearly three in every four people – reliant on humanitarian aid to survive. On top of this, dengue fever, malaria, diphtheria and cholera began to spread fast. 

Health system in Yemen has been facing many challenges in the last decade along with the complex emergency situation that includes widespread conflict-driven displacement and a slow-onset crisis in food security, malnutrition and outbreak of communicable diseases particularly in neglected areas. 

Malnutrition and extremes of ages make refugee population vulnerable due to low immunity, favourable environmental factors help in the creation and propagation of epidemics. 

Survival was a miracle not only because of endemic disease, dirt and filth, concomitant poor hygiene, and sanitation but also because of the primitive state of medical knowledge, thus, a large number of people were prone to infections for a sustained duration of time, within a constrained health system. 

The war-torn Arab country has also been suffering from a severe diphtheria outbreak. 

The disease, which has not been seen in Yemen for 25 years, has affected 312 people and killed 35.

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It has not spread explosively, as cholera did, but diphtheria outbreaks can affect many thousands, and there is a global shortage of diphtheria anti-toxin. 

Yemen has enough for 200 to 500 patients, Mr Poncin said. 

Ships and planes carrying humanitarian supplies have been unable to reach Yemen since the Saudi-led coalition imposed a blockade. 

In addition, recent heavy rainfall, disruption of water supplies and scarcity of safe drinking-water have contributed to the spread of mosquitoes in the affected areas, resulting in an upsurge in suspected dengue cases. 

WHO has also distributed information, education and communication materials to inform affected communities on how to protect themselves against dengue fever and other vector-borne and water-borne diseases. 

By December 2017, the outbreak of cholera in Yemen had infected a staggering million people. Despite being a completely treatable disease, thousands of people have died from the disease. 

More than 80% of Yemen's population lacks food, fuel, drinking water and access to health care services, which makes it particularly vulnerable to diseases that can generally be cured or eradicated elsewhere in the world. 

Cholera flared up in April 2016 and spread rapidly, killing 2,227 people, the death rate has fallen dramatically and, recent cases are probably diarrhoea, Mr Poncin said.