No 21 - 2016

Zika virus update
Serious outbreak of yellow fever in Angola

Zika virus update

Updated travel advice

It is now well-established that pregnant women (the foetus) are at special risk in case of Zika virus infection; and in accordance with the updated ECDC risk assessment from 20 May 2016 and the WHO´s travel recommendations, pregnant women and women who are currently considering pregnancy should postpone non-essential travel to areas with active Zika virus transmission, particularly travels to countries/areas with an increasing or widespread Zika prevalence (see list at the SSI website). If a journey cannot be postponed, the pregnant woman should be particularly attentive to prophylactic measures against mosquito bites.

Due to the risk of sexual transmission, men who return from areas with Zika virus outbreaks and who have a pregnant partner should use a condom for the remainder of her pregnancy. If the partner is of childbearing potential, but is not known to be pregnant, the man should use a condom for a minimum period of one month after returning. This applies regardless of whether he has presented with symptoms of Zika virus infection or not. Nevertheless, sexual transmission from symptom-free persons has not been described so far.

For more information about precautions for examination and diagnosis of returning travellers, please see The Danish Health Authority’s guideline of 25 May 2016 and EPI-NEWS 14/16.

The Olympics in Brazil

For travellers visiting the Olympic games in Rio in the summer of 2016, the ECDC has published a health risk assessment for travellers. It is assessed that the risk of being bitten by a mosquito and therefore of becoming infected with Zika virus or other mosquito-transferred conditions (dengue fever and chikungunya) is generally very low as the games coincide with the Brazilian winter in August/September. Nevertheless, the risk is higher in Manaus where a number of the football matches will take place. Even so, travellers should always use mosquito bite protection when visiting areas with a risk of Zika virus infection, i.e., all of Brazil. This will also protect the traveller against other mosquito-transferred conditions, including dengue fever and chikungunya. The main health risk for travellers visiting the Olympics is considered to be gastrointestinal infections due to poor food hygiene and infection with resistant intestinal bacteria.

Risk of transmission in Europe

On 19 May, the WHO published an assessment of the probability that local transmission will occur and that Zika virus outbreaks will affect Europe. The assessment is based on various factors: 1) if Aedes aegypti mosquitoes are present in the individual countries, 2) if the climate permits spreading of Aedes aegypti mosquitoes to the countries in question, 3) if there is a history of Aedes aegypti mosquitoes transferring virus conditions in the country, 4) if current Zika virus transmission is seen in a neighbouring country, and 5) the extent of air, sea and car traffic to the country. Furthermore, the assessment takes into account each country’s preparedness measures to fight mosquitoes and Zika virus. Generally, the WHO finds that in Europe the likelihood is only low to moderate, but with a high risk in a limited number of locations (Madeira and parts of the Black Sea Coast) where Aedes aegypti mosquitoes already occur. The risk in the Mediterranean countries is moderate, whereas the likelihood of local Zika virus transmission in Northern Europe, including Denmark, is considered to be low by the WHO.

At present, local transmission of Zika virus has not been observed in Europe; only imported cases have been recorded. The WHO report describes theoretical conditions related to any future transmission. Therefore, at present no recommendation is given for travels to Southern Europe or other parts of Europe with respect to the risk of Zika virus infection. It should be stressed that in Denmark there is currently no risk of Zika virus transmission as the Aedes aegypti mosquitoes that can transfer the condition are not found in Denmark. Nevertheless, the health authorities follow the development closely, including mosquito monitoring.

(A. Koch, L.S. Vestergaard, P.H. Andersen, Department of Infectious Disease Epidemiology)

Serious outbreak of yellow fever in Angola

A large yellow fever outbreak has developed in Africa in the course of the past five months, starting in Angola in Central Africa, but with international spreading, currently to three countries. The WHO describes the outbreak as the most serious outbreak observed in more than 30 years and expresses concern that the outbreak may spread to more large African cities.

The suspicion of a yellow fever outbreak in Angola was initially raised towards the end of December 2015 and the suspicion was confirmed by laboratory analysis on 20 January 2016. Subsequently, a considerable increase has been seen in the number of reported cases from several Angolan provinces. The outbreak is concentrated particularly on the major cities, including the capital of Luanda. The latest numbers from Angola show more than 2,400 suspected cases of which 735 are laboratory-confirmed, and approx. 300 deaths. Despite implementation of vaccination campaigns including more than seven million people in Angola, the yellow fever virus remains in circulation in several districts.

Furthermore, the outbreak has spread internationally. At present, three countries have reported of laboratory-confirmed yellow fever cases imported from Angola. A total of 42 imported cases were reported to have been imported to The Democratic Republic of Congo (DRC), two cases to Kenya and 11 cases to China. Subsequently, a local yellow fever outbreak of the same virus type as was seen in Angola was detected in the DRC, so far with a total of two confirmed cases and a number of suspected cases that are undergoing testing at present.

Uganda also recently recorded a large number of yellow fever cases, but laboratory analysis has demonstrated that these cases were not associated with the Angolan outbreak.

The observed imported yellow fever cases from Angola to other countries underline the risk of international spreading of the outbreak via non-vaccinated travellers. The outbreak can thereby spread further both to other provinces in the affected countries and to other African countries, particularly to the neighbouring countries of Namibia and Zambia. Due to limited monitoring systems in many areas, it is difficult to monitor and control the scope of the outbreak.

On 19 May 2016, the WHO held an Emergency Committee (EC) meeting in Geneva under the auspices of The International Health Regulations (IHR 2005). The EC meeting assessed that the current yellow fever outbreaks in Angola and the DRC constitute a serious public health threat that requires increased international action and international support. Nevertheless, the outbreaks are not currently considered to have reached the highest international risk level (”Public Health Emergency of International Concern”, PHEIC). But the WHO follows the development closely and assists the affected countries in their efforts to curb the outbreak.

The very comprehensive vaccination campaigns implemented in several African countries have put under pressure the global stock including the provision of yellow fever vaccines. This could potentially make it hard to curb the outbreak through mass vaccination campaigns in risk areas. In addition to Uganda, other countries have also observed minor local outbreaks of yellow fever, including Brazil and Peru in South America, but these outbreaks were not associated with the Angolan outbreak. Nevertheless, these isolated outbreaks underline the risk that yellow fever may spread among non-vaccinated population groups.

Danish travellers should be aware of the risk of yellow fever. Everyone, as from the age of 9 months, who will be travelling to countries where there is a risk of yellow fever should be vaccinated no later than 10 days before their departure and should bring their certified yellow fever vaccination card. For all travellers aged 9 months or older to Angola and the DRC, there is a requirement for yellow fever vaccination, even for persons travelling directly from Denmark; and the vaccine must have been administered no later than 10 days before entering the country. A complete list of the countries that require yellow fever vaccination when entering the country, for either all travellers or for travellers entering from areas with a risk of yellow fever transmission, is available here. For further information about yellow fever and for travel recommendations, please see the SSI website under Rejser og Smitsomme Sygdomme (in Danish), where you will also find a description of the Angolan outbreak.

(L.S. Vestergaard, P.H. Andersen, Department of Infectious Disease Epidemiology)

Link to previous issues of EPI-NEWS

25. May 2016