Confronting The Growing Risk From Zika
The entrance of homegrown Zika was inevitable. Florida was always going to be ground zero for its arrival. With proper vigilance, the expected outbreaks should be limited in number, and narrow in scope. That we’re nearing the end of summer should provide some bulwark against larger and more frequent occurrences.
Yet Zika’s predictable course provides limited comfort, in large measure owing to its worsening profile. The more we learn about the relatively new virus, the more dangerous it appears, especially to expectant mothers. There’s now firm evidence that the virus can impair the growth of a developing baby’s brain, especially during the first trimester of pregnancy, leading to a condition called microcephaly. It’s reasonable to worry that any virus powerful enough to cause these catastrophic outcomes may also have other untoward but more subtle effects on other babies.
Zika is an addressable threat. While it falls outside of the regular routine of public health preparedness, we shouldn’t be scrambling for new resources each time a threat like Zika starts to emerge. From West Nile to swine flu to Ebola to the global outbreak of dengue fever, the capacity to deal with threats like Zika must be designed into our preparedness posture. There should be an expectation that we have the existing apparatus to deal with these kinds of emerging threats. To tackle these risks, there are straightforward capabilities that we need to assemble.
Scientists studying yellow fever in Uganda’s Zika forest in 1947 first discovered the Zika virus in a monkey. But it wasn’t found to be actively circulating in people until a small outbreak was detected in 1962 in Africa. Once it recently became epidemic in South America, the U.S. mainland was vulnerable; especially Gulf states where the Aedes aegypti, the principal mosquito species that spreads Zika, is most prevalent.
So it should be no surprise that the Centers for Disease Control and the Florida Department of Health recently confirmed what we’ve been expecting: locally transmitted cases of Zika in Miami-Dade and neighboring Broward counties. All of the infections were apparently acquired in the same part of Miami. In addition to spreading through the mosquitoes, infected men can transmit Zika virus through sex. Zika survives in semen longer than in blood, but it is unclear for how long.
It’s likely that more cases of Zika will be diagnosed over the coming weeks. There will probably be other homegrown outbreaks in new parts of Florida and perhaps other states, where the infection can be spread to – and by – locally hatched mosquitoes. A number of U.S. states, especially in the Gulf region, have their own sizable populations of Aedes aegypti. The Aedes mosquito has long been notorious for transmitting yellow fever and dengue, which has become epidemic in South America. Over the years, Florida, Texas and Arizona have all experienced isolated outbreaks of dengue and yellow fever. Any of these states is also vulnerable to Zika.
The risk now is that, like the West Nile virus, Zika could become endemic to the U.S., with recurrent outbreaks each summer. Adding to this hazard, other mosquito species have also been shown capable of harboring Zika, including Aedes albopictus, which ranges across America as far north as Chicago and southern New York.
Putting in place the infrastructure to thwart Zika and similar mosquito-borne risks (including West Nile virus) should encompass five principles. First, better diagnostics to rapidly and accurately detect new infections; second, programs to collect and test mosquitoes to identify emerging outbreaks early; next vigilant mosquito abatement, and common-sense consumer precautions; and finally, a rejection of the impulse to magnify and misrepresent these events for political gain, which can – over time – dull public interest by conflating real and amplified risks.
On the issue of diagnostics, right now we lack effective blood tests to detect new infections at the point of medical care, in the doctors’ office. Blood tests need to be sent off to the CDC or a handful of state-run laboratories. They can take up to a week to return a result, require special handling and are still inaccurate. Primary care doctors are referring patients who want to get tested to special collection sites. There are practical and scientific limitations that make it hard to develop simple, rapid and accurate diagnostic tests. All of these challenges are surmountable.
Diagnosis can be challenging. The Zika virus can rapidly mutate. This makes it hard to develop DNA-based probes to test for active infection. The antibodies that the body develops after an infection has ensued, to attack the active virus, can be used to detect established infection. But these Zika antibodies can also be confused with similar antibodies left over from other mosquito-borne infections like dengue.
This limits the accuracy of the antigen-based diagnostics that work by detecting antibodies and are typically easier to develop and use. So complex confirmatory tests are required to diagnose Zika. These challenges limit the timeliness and utility of Zika tests and the number of labs that can perform them. It’s compounded by the fact that 80% of infections are silent, and cause a person no symptoms. So many people will never present with outward symptoms, or seek out a diagnosis.
Several tests that can be used in private, high-complexity molecular labs have recently received authorization by the Food and Drug Administration for “emergency use,” but not full FDA approval. These include a diagnostic test from Siemens Healthcare and similar tests offered by Hologic and Quest Diagnostics. But the tests work by detecting the presence of Zika virus in a patient’s blood by looking for Zika’s genetic material. They are only accurate when the patient has circulating virus in their blood, an initial period of infection that can last just days or weeks.
For these reasons, health officials should also have in place aggressive programs to monitor the local mosquito population, to test bugs for evidence of the virus. Florida has already invested heavily in these measures, as have other states, including New York and Virginia. Every vulnerable state needs to implement similar programs. Mosquitoes can be collected and tested to see if they’re carrying a virus like Zika. By implementing programs to catch and evaluate the insects throughout the affected regions, health officials can provide real-time information on emerging outbreaks.
This is what New York State did in response the outbreak of West Nile Virus in 2000. As I previously reported, during that summer, the New York State Department of Health implemented a program that collected 317,676 mosquitoes, submitting 9,952 pools of squashed mosquitoes for virus testing. Health officials found 363 pools of mosquitoes that tested positive for the virus, using a technology called polymerase chain reaction. This enabled state officials to get an early jump on quelling emerging outbreaks.
These same techniques can also be used to monitor for the spread of Zika virus. Rapid detection of the virus in field-collected mosquitoes can help focus mosquito control measures that could, in turn, prevent transmission among people.
This platform for early detection needs to be coupled to vigilant efforts to abate mosquitoes and common-sense precautions taken by consumers to avoid contact with mosquitoes. Some of the best mosquito repellents are the formulations that contain 20% picaridin (like the spray made by Sawyer) or 25%-30% DEET. The mosquito that most commonly carries Zika only ranges near to where it’s hatched, compared to other mosquito species that can travel as far as 30 miles. The average Aedes aegypti mosquito will travel no more than 500 meters in its lifetime. It’s most active during the day and especially active at dawn and at dusk. Containing outbreaks means detecting them early and eliminating the mosquitoes within the radius of infection. We should be up to this challenge.
Finally, confronting Zika will turn on our willingness to forgo the temptation to exploit or distort the risk for political gain. The Obama Administration has performed admirably in shunning political postures in the throes of other public health crises such as the outbreak of swine flu. Not so when it comes to Zika.
It seems unmistakable that the Obama Administration has tried to leverage wrangling over Zika funding for political advantage. They’ve used seemingly purposeful gridlock to bolster their political rhetoric accusing Republicans of inaction. Yet the House-passed Zika funding bill – supported by Republicans – was a reasonable compromise. But the White House and Senate Democrats summarily rejected it over outlying issues. Moreover, a lot of the needed funding for the current abatement measures was already available at the state level, and federally. The Department of Health and Human Services has $385 million in left over Ebola funds at its disposal. The money merely needed to be reprogrammed.
We need to be more willing to leverage existing funds to deal with these sorts of medical contingencies, and not turn each one into a political and budgetary showdown. These infection risks are the new normal. We should not have to treat our response to each outbreak as a new disaster and lurch from one crisis to the next. For longer-term planning, such as investment in a Zika vaccine, the President’s take-it-or-leave-it approach to his Zika funding package was without precedent.
A sense of urgency about yellow fever fueled efforts in the 20th century to eliminate the Aedes aegypti mosquito in South America, using the same strategies that we now must adopt to contain Zika’s spread. Although successful in clearing Aedes aegypti from most of South America, the yellow fever programs were not sustained. The mosquitoes returned, only to spread this new contagion.
When it comes to mosquito-borne risks, the battle plan was written long ago and employed with success. Zika is a new infection, but not a new kind of risk. What can we learn from these experiences? We can’t afford to play catch-up every time a new infection appears. The policy and infrastructure should already be in place.
This article was written by Scott Gottlieb from Forbes and was legally licensed through the NewsCred publisher network.
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