No 12 - 2017

New country classification for Zika virus

In collaboration with the ECDC (the European Centre for Disease Prevention and Control) and the US CDC (Centers for Disease Control and Prevention), the WHO has introduced a joint classification of countries with respect to the risk of Zika virus infection as from 10 March 2017. The classification divides the countries into four groups based on both current and previous occurrence of Zika virus as well as the potential for infection with Zika virus assessed on the basis of the presence of relevant mosquitoes, among others.

Category 1 includes countries/areas with ongoing Zika virus infection, and where Zika virus is either newly introduced (from 2015 onwards) of re-introduced. This category largely corresponds to the countries/areas that have so far been listed on the Statens Serum Institut (SSI) website as countries/areas with Zika virus outbreaks. Pregnant women and women who are currently considering pregnancy are recommended to postpone any non-necessary travels to Category 1 countries.

Category 2 includes countries/areas with ongoing Zika virus infection, where Zika virus was present before 2015, or where Zika virus is no longer newly introduced or re-introduced. Currently, this category includes countries where Zika virus infection was observed before 2015, including some countries in Africa and Southeast Asia.

In addition, this category will, in future, include countries from Category 1 in which transmission continues to occur after a prolonged period of time, probably around 2 years. This may include some countries in South and Central America, for instance. Countries in this category are considered Zika virus endemic. If pregnant women travel to these countries, they should be extra careful to protect themselves against mosquito bites; see below.

Category 3 includes countries/regions where infection with Zika virus is not currently ongoing, but has occurred in the past, and where there is a potential for infection in the future. This currently includes only a limited number of countries/areas of limited size such as the Easter Island and some other Pacific islands.

Category 4 includes countries where the mosquito that typically transmits Zika virus (Aedes aegypti) occurs, which therefore have a potential for infection, but where local cases of infection with Zika virus have not been recorded. This includes a number of countries on several continents.

The new country classification can be accessed at the SSI’s Zika virus outbreak page. Here, you will also find further advice on Zika virus.

The SSI's recommendations for travel to areas with Zika virus, and in particular for pregnant women, remain essentially unchanged. Pregnant women and women who are currently considering a pregnancy are still recommended to postpone any non-necessary travels to Category 1 countries. If a journey cannot be postponed, the pregnant woman should be particularly attentive to prophylactic measures against mosquito bites.

Generally, everyone - and pregnant women in particular - who travel to areas with a risk of mosquito-borne conditions are recommended to protect themselves sufficiently against mosquito bites. See protection of pregnant travellers (in Danish language) at the SSI’s website.

Even though the WHO, the ECDC and the CDC have prepared the new classification jointly, the lists of countries with Zika virus outbreaks that are available on each organisation’s website are not yet fully identical, and some variation may be seen between each organisation’s travel recommendations. This may, among other things, be due to local assessments.

Statens Serum Institut continuously monitors the situation. The Institute’s current travel recommendations are provided on the Zika virus outbreak page.

(A. Koch, P.H. Andersen, P. Valentiner-Branth, Department of Infectious Disease Epidemiology and Prevention)

Extended yellow fever vaccination recommendations for travels to Brazil

The yellow fever outbreak in Brazil, EPI-NEWS 6/17 and 10/17, is still spreading to new areas, which are usually not considered yellow fever risk areas. Reports have been made of confirmed cases of yellow fever in the state of Rio de Janeiro and suspected cases in both primates (apes) and in humans in the state of São Paulo. However, at present no cases have been reported from the cities of Rio de Janerio or São Paulo.

In view of the uncertain situation and after consulting with its Travel Reference Group, the SSI has decided to recommend yellow fever vaccination until further notice for all travellers to Brazil who are more than 9 months old. There is still no requirement for yellow fever vaccination when entering Brazil.

The vaccine may be given as from 9 months of age. Protection becomes effective as from 10 days after vaccination. The vaccine is administered as a single dose. A single vaccination provides lifelong protection. This also applies to persons who have previously been vaccinated against yellow fever.

(P.H. Andersen, A. Koch, Department of Infectious Disease Epidemiology and Prevention, the SSI’s Travel Reference Group)

Link to previous issues of EPI-NEWS

22 March 2017