There are rising concerns that a yellow fever epidemic in Africa could spread into neighbouring countries and develop into a global health emergency. The World Health Organisation is monitoring the yellow fever outbreak in Angola, which is spreading into neighbouring countries, so far Kenya, Uganda and the Democratic Republic of Congo have all reported cases.

The current yellow fever epidemic is the worst outbreak of the disease in Angola since 1986. Millions of people could potentially be at risk from the disease if it spreads throughout Africa and Asia; health professionals are urging the WHO to declare an emergency and act now. Concerns are also being raised about a lack of vaccines to treat an outbreak.

Yellow fever is caused by a virus carried by Aedes mosquitoes, it is not passed from person to person by close contact. It is found in the tropical regions of Africa and the Americas. The first symptoms of the disease usually appear 3–6 days after infection, and include fever, muscle pain, headache, nausea and vomiting. After 3–4 days, most patients improve and symptoms disappear.

However, in a few cases, the patient can become severely ill again as the disease enters a “toxic” phase: fever reappears, and the patient develops jaundice (hence the name yellow fever) and sometimes bleeding, with blood appearing in the vomit. About 50% of patients who enter the toxic phase die within 10–14 days. There is no specific treatment for yellow fever but there is a vaccine that can prevent infection.

Health officials are concerned an outbreak in Africa could spread to other continents like Asia and South America, as is happening with the Zika virus, and even to some parts of northern Asia and Europe. There has been a surge in new infectious diseases in recent years, thought to be driven in part by climate change, so there is a growing call for the WHO, and similar organisations, to react to the problem and set up a permanent committee to decide how to respond as new threats emerge.

Since the 1980s, a number of new disease threats have been identified:  Middle East Respiratory Syndrome (MERS), Severe Acute Respiratory Syndrome (SARS), West Nile virus, bird flu and swine flu. A range of reasons are thought to be behind this; a rise in the human population, increase in the number of people flying abroad allowing viruses to spread around the globe, climate change and loss of animal habitats that has forced them to come into closer contact with humans increasing the risk of viral transfer.

Scientists are concerned that yellow fever could even reach Europe as the climate gets warm enough for Asian tiger mosquito to flourish. The insect has spread from its native territory in south-east Asia to Europe in just 20 years.

There are also concerns about a potential shortage of vaccines. Mass vaccination campaigns would be needed to prevent spread of an outbreak and increase in vaccine production is needed to be prepared for such an eventuality. It is being argued by many organisations that in view of the increasing threats from new diseases and potential pandemics the WHO now needs to set up a permanent body to monitor outbreaks and mobilise funds, and co-ordinate international responses to identify, prevent and prepare for potential epidemics.

The WHO, which said last month that yellow fever was a threat to the entire world, said that holding an emergency committee meeting on yellow fever was “under discussion”. WHO is also helping Angola and DRC to carry out mass immunisation campaigns in the affected areas, detect new cases, and control mosquitoes and other disease vectors. On its website, WHO warns about yellow fever:

“The risk of international spread is greater than before. In the past devastating outbreaks occurred mainly in sea ports. Today, most cities are connected to most of the world by more rapid means of transport, train or plane.”

People travelling from the UK are advised to seek medical advice before travel and ensure they have the yellow fever vaccine if they are travelling to parts of the world affected by the disease.

Rachel Kayani