UPMC doctor: Stop Zika at its source — the mosquito
Before the past few weeks, Zika virus was not something on the radar of most Americans, but it is now the subject of headlines warning of devastating complications in the fetuses of pregnant women. Post-Ebola, many infectious diseases prompt doom-and-gloom headlines that do not provide full context and threat analysis — an essential process to help the general public determine the level of concern they should have.
Zika virus is not a new virus. It was first discovered in the 1940s in the Zika Forest, for which it is named, in Uganda. The virus is part of the same group of viruses that include the much more familiar viruses that cause yellow fever, dengue, and West Nile fever and, like them, is transmitted by mosquitoes. Aedes mosquitoes, the same mosquito type that spreads dengue, yellow fever, and the unrelated chikungunya, are the vectors for Zika.
For the vast majority of people, Zika is not a dangerous disease. In fact, 80 percent of those infected have no symptoms at all. Of those who become symptomatic, fevers, chills, headaches, rash and muscle/joint pains last about a week and then dissipate. Given those facts about Zika, it is not surprising that it was not considered a major public health concern but more of a piece of travel medicine trivia.
Prior to the current South American outbreak, Zika had caused several smaller scale outbreaks scattered across Africa and Asia. In 2007, a notable outbreak, small in comparison to the South American situation of today, reached more than 100 confirmed and probable cases in Micronesia. This outbreak forms the basis of much of what we know — and don’t know — about Zika.
In May, alerts were issued regarding the detection of Zika virus in Brazil. This outbreak has spread to many more places in the region, including Puerto Rico and the U.S. Virgin Islands. Concomitant with the large number of confirmed Zika cases in Brazil — which number more than 500,000 — was a large increase in the number of microcephaly cases in fetuses and newborns. Microcephaly refers to a condition in which a fetus or baby has an abnormally small head. This devastating condition, which can be diagnosed via ultrasound, can shorten lifespan, cause developmental delay and lead to intellectual disability. Additionally, some babies have hearing and eye problems that may be the result of Zika. This association is strengthening, but will not achieve, the level of a causal link until more scientific studies are performed that assess whether other infectious, nutritional or prenatal factors have a role. The same can be said about the possible link with the autoimmune neurologic disorder Guillian-Barre Syndrome.
Aedes mosquitoes abound in this hemisphere and inhabit a large swath of the United States. Aedes aegypti is the primary mosquito responsible for transmission in the current outbreak; however, Aedes albopictus, the Asian tiger mosquito, also is able to transmit the virus and did so in a 2007 outbreak in Gabon. Aedes albopictus has a wider geographic range than Aedes aegypti and even reaches to southeastern Pennsylvania.
Because there is no vaccine against Zika (and one is not expected to be available for some time) the chief means of prevention are to attack the mosquito vector. This type of strategy has been used for decades against Aedes mosquitoes to control dengue and yellow fever and involves a whole host of activities, some of which my colleagues and I described in research conducted on past dengue outbreaks in Florida, Hawaii and Texas. Chief among these activities is removing standing water in which the Aedes mosquito lays eggs. Receptacles that harbor standing water are often found on the grounds of private residences, necessitating the engagement of individual residents to police their own property. Genetically modified mosquitoes are a promising new technology likely to be deployed in this fight to reduce mosquito populations as well.
In the coming days, there will be reports of Zika virus being confirmed in U.S.-based travelers all over the country as testing is ramped up. This is nothing new (although the numbers will be higher due to increased awareness and the proximity of the outbreak). Even prior to this outbreak, Zika virus had been confirmed in Americans who had traveled to areas in which the virus was present. Clinicians will need to remain alert to this possibility and, as they should as a matter of routine, assess the travel history of patients, not just for Zika but for a whole host of travel-related infections that are a continual risk.
Zika’s spread in this hemisphere, coupled with the potential role it may play in severe pregnancy complications, will challenge public health authorities. A swift and effective response to this infectious disease emergency, directed against an old mosquitoes foe that has plagued humans for centuries will be the key to minimizing the impact of Zika.
Dr. Adalja is an infectious disease physician at UPMC, a senior associate at the UPMC Center for Health Security, and a spokesperson for the Infectious Disease Society of America. Follow him on Twitter: @AmeshAA.