Zika Virus Advice for Mountaineers: A UIAA Medcom Consensus Advice Sheet

Introduction

In the past few weeks, the media has led with stories of increasing awareness that infection with the Zika virus may be linked to an increase in children being born with birth defects such as microcephaly in some South American countries. This advice sheet is approved by the UIAA Medcom and is based on the current best advice from the UK's National Travel Health Network and Centre (NaTHNaC), NHS Scotland, The World Health Organization (WHO), The Pan American Health Organization (PAHO), the Centers for Disease Control (CDC) in the United States, and the Robert Koch Institute in Germany.

Disease Background

The Zika virus was first identified in Africa in 1947 and first confirmed in humans in 1952. It is transmitted by the bite of a mosquito, a bit like dengue fever and malaria. Only about one in five people infected actually show any symptoms, which are those of a vague self-limiting flu-like illness often with associated red eyes (conjunctivitis). In the past few months, evidence has begun to appear that if a nonimmune pregnant woman becomes infected, it may lead to potentially very serious defects in fetal brain development. It is uncertain whether it may cause other fetal defects. It is likely that the risk is greatest if one is infected in the first trimester of pregnancy, possibly even before a woman may realize she is pregnant. Cases of resultant Guillain Barre syndrome are also documented, although very rarely, in infected men and women.

This Aedes mosquito-transmitted infection has been found in Africa and Asia, but at the moment, possibly linked, birth defects have mainly been identified in a few countries in South and Central America; however, we can expect more cases to come to light as testing and awareness increase. It is very likely to spread to neighboring countries where the Aedes mosquito vector is prevalent.

Relevance to Climbers and Mountaineers

Like the malaria mosquito, the Aedes mosquito cannot survive in cold climates at altitudes, but travelers must take into account the risks of bites during transit. It is very unlikely that the mosquito can survive above 2500 m.

Two cases of sexual transmission from an infected man to his partner have been documented and the virus has been identified in semen samples.

Women above childbearing age who have chosen sterilization as a method of contraception or who are infertile are obviously not at risk from the pregnancy point of view.

For women of childbearing age, the picture is still confused with different authorities giving different advice. This advice sheet may be found to be over cautious and research is ongoing. Despite comments in the media, the connection between birth defects and Zika infection has not yet been definitely proven, although it does seem likely. There is no vaccine available and one is not likely to be developed in the near future.

Current Advice

With no known treatment for the mild flu-like illness of Zika infection, the best precaution for both men and women is to avoid mosquito bites. Travelers know that to avoid being bitten is difficult, but some people are not as aware of bites as other more sensitive people. For women at risk of pregnancy, some authorities suggest they should avoid travel to all risk areas. If travel is deemed essential, we would recommend the following minimal precautions:

(1) Effective contraception.

We would recommend being established on a reliable method of contraception for at least 2 months before departure to any affected country, while away and for at least 3 months after return, especially if traveling to places below 2500 m altitude. For advice on contraception at altitudes more than 2500 m, see the UIAA Medical Advice sheet at: www.theuiaa.org/medical_advice.html

It is suggested that any male returning from a trip through a risk area should avoid fathering a child for at least a month after return and that any infected male should use condoms for 6 months

Updated Information Sources

With any evolving infection with international implications, information is constantly evolving and being updated. We suggest the following reliable websites: www.who.int/mediacentre/factsheets/zika/en; www.cdc.gov/zika