By: Dr. Frank MacMillan – June, 2016
It seems like each year brings a new infectious disease worry, last year it was Ebola virus, this year it is Zika virus. Don’t underestimate the economic impact though. There is speculative talk about cancelling or moving this summer’s Brazil Olympic Games. Years in planning and billions of dollars are at stake. The way the news cycle seems to work, anything sensational like this is guaranteed to be over exposed to maximize ratings. The public health stakes are potentially very high too. We should not let this anxiety lead us to do things that are impulsive. So let’s try to educate ourselves and be smarter about what we can and should do.
First, Zika virus is not something new. It was discovered in a Rhesus monkey in the Zika rain forest, Uganda in 1947.The first human case was reported in 1952. It was originally limited to Africa, but has spread to South Asia and the South Pacific islands over the past several decades. On the islands in particular, an outbreak would be limited by the small population and the rapid acquisition of population immunity. The virus reached the Americas first in Brazil, and has since spread into Central America, Mexico, and into the Caribbean, including Puerto Rico, Hispaniola and the US Virgin Islands. It is a mosquito borne virus, and the most important species vector is the Aedes aegypti mosquito. This is a tropical mosquito, which is also found in the US mainland bordering the Gulf of Mexico. We have a different Aedes species in New England which is believed to also be capable of transmitting the virus Aedes albopictus, which can also transmit West Nile and Eastern Equine Encephalitis viruses. These tropical and subtropical mosquito species have moved around the world because of trade and travel, and this has helped spread the diseases they carry as well.
So far on the US mainland, Zika has been found exclusively in travelers. We have learned some new things about this virus. Typical symptoms may include fever, joint ache, muscle ache, raised red rash, headache, conjunctivitis, and muscle weakness, though most will not have any viral syndrome at all. According to the CDC, the mean time the virus can be detected in blood after infection is three days. The virus has also been found in saliva, urine and semen, and can cross the placenta in a pregnant woman to infect her developing child. The virus may cause severe brain injury in the developing fetus, resulting in microcephaly (unusually small head because brain development is impaired). Microcephaly is the most feared complication, because it can result in death or permanent disability. The virus can also cause blindness, and in a small number of adults, there have been reports of Guillain-Barre Syndrome (a paralysis syndrome similar to Polio).
Current knowledge tells us that neurologic symptoms and injury do not occur in all people infected, and that virus can be cleared by our immune systems by neutralizing antibodies, implying a potential for vaccine development. Currently there is no vaccine or antiviral treatment, so the people who are most at risk should take precautions. They include pregnant women, the very old, very young, and the chronically ill. Simply avoiding travel to affected areas by those at highest risk, using air conditioning and screened windows at home, dressing in long sleeves and using insect repellant when out of doors can prevent infection.
Public health interventions may include mosquito traps, which have been effective in reducing the transmission of Chikungunya virus in Puerto Rico, another nasty tropical virus transmitted by the same Aedes mosquitos, and draining water where the mosquitos breed, like birdfeeders, abandoned swimming pools, discarded automobile tires, and the like. Many of the interventions that we already use for Eastern Equine Encephalitis and West Nile Virus like larvaciding storm drains and spraying are potentially effective additional tools that can be adapted to Zika.
It is not a matter of if the Zika virus is coming to the US mainland, but a matter of when and how well we will be prepared. We live with lots of other insect and tick borne diseases, and we are learning how to better manage and reduce transmission all the time. This is a nasty virus, and there will almost certainly be new ones to follow. It is not time to panic, but time to get smart and prepare. Infectious diseases will always be among us. Preparation can help to keep us a step ahead.