Beware of Yellow Fever

I have written on the topic of yellow fever at least twice before. The first time was when the outbreak in Africa sparked global public health attention and then, subsequently on the outbreak in Brazil. It is fitting for me to once again address this very important public health topic, as the threat of this mosquito-borne disease gets closer and closer to us.

Yellow fever is an acute viral haemorrhagic disease, transmitted by infected mosquitoes. The “yellow” in the name refers to the jaundice that affects some patients who contract the virus. Symptoms of yellow fever include fever, headache, jaundice, muscle pain, nausea, vomiting and fatigue. A small proportion of patients who contract the virus develop severe symptoms and approximately half of those die within seven to 10 days.

There are concerns with cases of yellow fever being reported in South America. The cases that have been reported are not in urban areas and are confined to forested areas. However, there is potential that these outbreaks can spread to urban areas. Once transmission occurs in urban areas, the virus can be transmitted by the Aedes mosquitoes.

Large epidemics of yellow fever occur when infected people introduce the virus into heavily populated areas with high mosquito density and where most people have little or no immunity, due to lack of vaccination. In these conditions, infected mosquitoes transmit the virus from person to person.

The Caribbean region is very vulnerable, as we have seen over the past years how quickly mosquito-borne diseases have spread through the region. In 2014, an outbreak of Chikungunya ravished the region and even before we could recover, Zika appeared. We are still dealing with this troubling disease.

There have been calls to ban the movement of people coming from countries that are considered “at risk” for yellow fever. The introduction of bans will not work, because our people travel to these areas and may not be immunized and can bring back the disease.

Whilst a ban may prevent travellers coming directly from one country, travellers generally move about and may travel from one country to three or four other places before entering their final destinations. A ban will be going against what is laid out in the international Health Regulations (IHR) and will disrupt the free movement of people and cargo.

There are public health measures that are more effective that can protect our people. Surveillance of vector borne diseases must be strengthened. There is the need to develop an active dengue-CHIKV-ZIKA and Yellow Fever Surveillance system. Public health surveillance at points of entry must be developed and must work effectively.

There is the need for a strong public awareness campaign to educate the population, not only on yellow fever, but on ways to eliminate the Aedes aegypti mosquito. There is also the need to let citizens know if they are travelling to certain places they must be vaccinated. These places must be clearly identified by public health authorities and must be made public. Travellers to these areas must show

certificate of immunization to exit. The public health act must be strengthened to hold accountable those who breach such orders.

In terms of entry requirements, there must be clear definition on who is required to show the certificate of vaccination. Clear guidelines must be published and this must be available to all travellers. There is the need to work with the tourism industry to ensure that this is communicated to both flying and cruise passengers.

We do not need to vaccinate our entire country, since the risk may be low now, but we must ensure that there is a stockpile of vaccines, in the event there is the need for mass emergency immunization.

Yellow fever is prevented by an extremely effective vaccine, which is safe and affordable. A single dose of yellow fever vaccine is sufficient to confer sustained immunity and life-long protection against the disease and a booster dose of the vaccine is not needed. The vaccine provides effective immunity within 30 days for 99 per cent of persons vaccinated.

Good supportive treatment in hospitals improves survival rates. There is currently no specific anti-viral drug for yellow fever.

No ban is needed; instead surveillance, vaccination and public awareness must be instituted and must work hand in hand.

Dr. Rosmond Adams, MD is a medical doctor and a public health specialist with training in bioethics and ethical issues in medicine, the life sciences and research. He is the head of Health Information, Communicable Disease and Emergency Response at the Caribbean Public Health Agency (CARPHA). He is also a member of the World Health Organization Global Coordination Mechanism on the Prevention and Control of NCDs.

(The views expressed here are not written on behalf of CARPHA nor the WHO)

Dr Rosmond Adams is a medical doctor and a public health specialist. He may be emailed at:adamsrosmond@gmail.com