Much has rightly been written about the Zika virus in the last few months, yet still we see a number of misunderstandings, rumors, and fears about potential risk, being propagated widely through the media.
Each day brings new developments and expert opinion on the subject, but also, more speculation and subterfuge, with prophylactic advice varying from travel bans, mosquito repellents, contraception, and even abstention from pregnancy.
A crucial factor amplifying this trend, and perhaps the elephant in the room, is the impending 2016 Rio Summer Olympic games. With the world’s eye soon to be focused on Brazil, there is clearly a demand from governments, companies, and other interested parties to ensure they safeguard their respective populations as best they can. Unfortunately, this also means we have seen a number of them act too hastily in their assessment of the risks presented by the Zika virus.
So, what are the risks? Well, we know for sure that there is no vaccine, and it is unlikely we will see one developed this year. But the risk to adults and healthy individuals is still relatively small, as symptoms of Zika virus infection are comparable with the common cold – and certainly not life threatening or even highly infectious in the way prior tropical diseases from Africa, like Ebola, have been. In fact, Zika remained an “unsexy” and largely forgotten virus until we saw the recent probable linkages with microcephaly.
The greatest risk currently recognized is clearly to women who are pregnant or are planning to be pregnant in the near future, and at this point, we believe the risk is probably greatest in the first trimester. This is obviously a major challenge for the domestic populations of Latin America, especially when it is at present unclear whether there is any risk in asymptomatic cases of Zika. From the information we have, and until a fuller understanding of the virus risk is known, it appears that the strongest link of microcephaly presents in cases in which patients have shown symptoms; however, 25% of the mothers of babies with microcephaly remain without any symptoms. And this is, of course, a situation made even more complex by the religious elements of society in South America, where contraception remains enshrouded in cultural stigma and abortion is illegal in many countries – even in those with cases of known prebirth microcephaly.
With no vaccine on the horizon and no cure or effective treatment once infected, clearly, the only viable preventive technique is to cut the spread of the virus. In this case, we must look to reduce the vectors of this disease – namely the Aedes aegypti mosquito. This particular type of Aedes mosquito is prominent throughout tropical regions – namely much of Latin America, South Asia, around the Gulf coast, and in isolated pockets near the Black Sea in Europe. In terms of the virus and the regions in which it has been found, most cases appear in the Latin American mainland, the Caribbean, and Cape Verde – although it may be just a matter of time before it spreads into the Aedes aegypti mosquito’s other habitats within Africa and even Asia. And, of course, it is essential we continue to investigate how viable a vector other species of the Aedes mosquito may be.
Despite these concerns, the risk in terms of the 2016 Olympics, especially for traveling populations, remains low – with the notable exception of pregnant women. In fact, the U.S. Centers for Disease Control and Prevention recommends that any travelers who are pregnant (at any stage/trimester) or planning to become pregnant, should avoid traveling to areas with Zika virus outbreaks. If they cannot avoid travel or if people live in areas where Zika virus transmission is known to occur, meticulous efforts to avoid mosquito bites during both daytime and nighttime hours must be adhered to. While it may sound a rather low-tech solution for modern health care, pregnant women in Zika-affected areas should wear protective clothing, apply a U.S. Environmental Protection Agency–approved insect repellent, and sleep in a screened room or under a mosquito net. However, it is also important to note that the Aedes aegypti mosquitoes predominantly bite during the day, especially around dawn and dusk, and therefore the correct timing and use of mosquito repellents and other personal protection measures are essential.
One final important point to emphasize is that contraception for travelers during the Rio Olympics, and when they return home, is another area of vigilance. By this, we mean both men and women, as evidence suggests Zika may be able to survive in semen for up to 1 month after infection – some reports even suggest cases of Zika remaining in semen for several months. However, the advice remains the same, if you were symptomless, then 1 month of condom use after your return will be enough to mitigate the risk of infection to a sexual partner, and 6 months after return for those who have symptoms.
The obvious unknown is the symptomless cases: Can the virus remain transmissible after the return of an athlete or visitor to the games? This is a crucial point and helps explain where there are still a number of misunderstandings. While in Brazil’s population there are some symptomless cases, people from abroad with no prior exposure to Zika virus (and therefore no resistance), would certainly have some symptoms. This remains true for both North Americans and Europeans, and so they are at no risk of further spreading the virus 1 month after their return from Brazil – should they not present any symptoms.
In one recent case of overkill, Kenya threatened to boycott the Summer Games entirely on safety grounds, a move clearly based on no identifiable scientific evidence, as the risk for athletes alone remains very low and fundamentally manageable. Conversely, the other controversial advice I have recently seen stems from the World Health Organization itself – which suggested women in Latin America should not put off pregnancy for fear of Zika. But until more information is known, and the RNA is properly analyzed or a vaccine becomes available, this is not a position I can yet support. We need to fully understand the risks of Zika virus infection, and there is still a long way to go.
Prof. Dr. Eskild Petersen is a member of the European Society of Clinical Microbiology and Infectious Diseases ( ESCMID ) study group for Infections in Travellers and Migrants ( ESGITM ) as well as a professor of tropical medicine at Aarhus University Hospital, Denmark, and senior consultant of infectious diseases at the Royal Hospital, Muscat, Oman. He has undertaken work on infectious diseases, clinical immunology, and tropical and travel medicine. His recent research focuses on the rapid spread of Zika virus in the Americas and the implications for the 2016 Rio Olympic Games.
