By Richard Knox
The World Health Organization on Monday declared a “Public Health Emergency of International Concern” because of a fast-moving outbreak of serious birth defects and some cases of adult paralysis that appear to be connected to the Zika virus.
WHO Director-General Margaret Chan said the situation represents “an extraordinary event and a public health threat to other parts of the world.” The agency says a previously obscure virus has spread to 25 countries and territories in this hemisphere so far.
The declaration comes before definitive proof that the birth defects and neurological illness, called Guillain-Barre syndrome, are caused by the mosquito-borne virus. But Chan said it would be a mistake to wait until a causative link has been proven — or disproven.
“Can you imagine if we did not do all this work now, and waited until the scientific evidence comes out, then people would say…’Why didn’t you take action? Because the mosquito is ubiquitous,'” Chan said.
The WHO declared a similar emergency last year because of Ebola in West Africa — but was heavily criticized for waiting too long in that case.
About 4,000 children have been born in Brazil recently with microcephaly, a stunting of the brain and skull associated with severe cognitive defects — a 20-fold increase over the past year. Of these affected infants, 270 were born to mothers who had confirmed exposure to the virus. Brazilian officials estimate that four million people there could be infected with Zika in the coming year.
A declaration of public health emergency allows the WHO to release contingency funds to help affected countries track and count cases, explore the possible viral link, help develop a diagnostic test and possibly a vaccine, and intensify efforts to control the mosquitoes that transmit the Zika virus. The WHO does not recommend restricting travel to affected areas, though the Geneva-based agency reiterated its advice to pregnant women to avoid travel to areas where Zika virus is spreading.
Experts say it could take six to nine months to determine if Zika virus is responsible for the explosive increase in microcephaly and occasional cases of Guillain-Barre syndrome. That’s too long to be certain before next July’s Olympics in Brazil, ground zero of the Zika outbreak.
But increasingly few experts doubt that link. There appears to be no other good explanation why Brazil’s tally of microcephaly cases has ballooned from fewer than 200 in 2014 to more than 4,000 since then, while Zika infections in Brazil soared from zero to 1.5 million.
The rapidly evolving picture is not simple. On one hand, the World Health Organization calls the spread “explosive.” In just a few months, the virus has infiltrated 23 Latin and Central American countries. And there seems every prospect that Zika could become endemic in this hemisphere — that is, that it could be around for years to come.
“Zika is here to stay in the Western Hemisphere,” Michael Osterholm, of the Center for Infectious Disease Research and Policy at the University of Minnesota, wrote in The New York Times this weekend. “It will be part of life for many years to come.”
This Pandemic ‘Is Truly Remarkable’
At the same time, health officials and some academic researchers — such as medical geographer Jared Aldstadt at the University at Buffalo — say they’re confident the U.S. mainland will escape anything like the outbreaks below our southern borders. They do predict localized outbreaks in southern Florida and Texas, where the Aedes aegyptus mosquito that carries Zika commonly breeds and bites. Twenty cases of Zika have been confirmed so far in Puerto Rico and the U.S. Virgin Islands.
Complicating the picture further, officials predict many isolated cases of Zika infection on the U.S. mainland among travelers — like the Boston man who last week was reported to fall ill after returning from a Zika-affected country. So far, nearly three dozen cases in 11 states have already popped up. The U.S. has also seen several cases of Zika-associated microcephaly involving infants born to mothers infected in other countries.
So why don’t U.S. health authorities sound more worried? They say they don’t expect Zika to spread widely here because we fight mosquitoes better. Most Americans have screens or air conditioning to keep infected mosquitoes away, and this country generally has good mosquito control programs. Also, most of the country lacks the kind of Aedes aegypti mosquitoes that can carry the virus, which is now present in 11 mostly southeastern states. However, as I’ll address below, that could change.
The stark reality is that in this hemisphere Zika is already pandemic — that is, an outbreak that occurs over a wide area and affects a substantial proportion of a population. That’s a surprise even to the world’s leading experts on emerging infections, since Zika had flown under the radar for the 67 years since its discovery in the Ugandan jungle.
“Its current explosive pandemic reemergence is…truly remarkable,” Drs. Anthony Fauci and David Morens, of the National Institute of Allergy and Infectious Diseases, wrote in the Jan. 13 New England Journal of Medicine. They ascribe that to “urban crowding, constant international travel and other human behaviors” that “can cause innumerable slumbering infectious agents to emerge unexpectedly.”
Such awakened viruses can tear through a population that’s never been exposed before and has no immunity – one powerful factor behind Zika’s explosive spread.
We’ve Been Here Before — With Rubella
This isn’t the first time a “birth defect virus” has swept the world.
In 1964-’65, the United States suffered an epidemic of a virus called rubella, once called German measles, that infected more than 12 million people. Twenty thousand U.S. babies were born with congenital rubella syndrome. Eleven thousand affected children were born deaf, 3,500 blind, 1,800 suffered severe brain damage. Thousands more either died in infancy or were aborted.
The rubella threat began to decline even before the first vaccine was licensed in 1969, but it wasn’t until 2004 that the disease was officially eliminated in this country. For the entire hemisphere, that landmark was reached only last April. Elsewhere in the world, more than 100,000 rubella-damaged babies are born every year.
So far the evidence suggests Brazil, and very likely other countries among the 23 where Zika is circulating, may face a birth defects disaster of similar scale. Microcephaly may be just the tip of that iceberg.
“The concern is that Zika virus damage is very likely not limited to microcephaly,” said Dr. Ernesto Marques, who splits his time between Brazil and the Center for Vaccine Research at the University of Pittsburgh. “Microcephaly is the easiest one to track at this point. But it has been observed that some other malformations, such as of the hands and feet, are increasing.”
In the case of congenital rubella, the devastation didn’t end until an effective vaccine was invented and achieved near-universal application. (The vaccine is part of the measles/mumps/rubella shots that children now get at around 12 months and again between ages 4 and 6. )
The Vaccine Challenge
But it will be years before a vaccine starts preventing Zika-associated birth defects.
“Prior to this time, we haven’t spent anything on Zika virus,” Fauci, the NIAID director, said at a briefing for journalists last week.
That doesn’t mean researchers are starting from zero to make a Zika vaccine. Fauci says his institute plans to insert Zika virus genes into a DNA backbone that has already been used to make a successful vaccine against West Nile virus — another mosquito-borne infection that causes more than 2,000 reported U.S. cases and 119 deaths a year.
Fauci says the West Nile-adapted Zika vaccine may be ready for preliminary human trials later this year. But, he added, “We will not have a widely available Zika virus vaccine this year or even in the next few years.”
Even when the monumental, expensive Zika vaccine project is finished, there’s the complicated problem of how to deploy and pay for the vaccine.
“Preemptively vaccinating large populations in anticipation of outbreaks may be prohibitively expensive and not cost-effective,” they warned in the New England Journal. “Yet vaccine stockpiling followed by rapid deployment may be too slow to counter sudden explosive epidemics.”
Since Zika infections are generally mild in adults, there wouldn’t be much justification to vaccinate the general population — and people might not be enthusiastic about getting vaccinated. Marques, the Brazilian public health expert, thinks young girls would be targeted to make sure they’re protected before they reach child-bearing age.
What Can Be Done About Zika Now?
But all that is in the indefinite future. Right now the options for limiting Zika infections and their damage to unborn children are sharply limited and highly imperfect.
It comes down to two things: killing mosquitoes that carry Zika and educating people to do what they can to avoid being bitten — mainly wearing long-sleeved clothing and pants and using mosquito repellent.
Mosquito abatement involves spraying insecticides and eliminating standing pools of water where mosquitoes breed. That task is made more difficult by torrential rains caused by the current El Nino effect. And the problem has been amplified enormously by the spread of non-biodegradable plastic and rubber waste that collects rainwater and gives mosquitoes countless opportunities to breed.
“Mosquito control in urban areas is not easy to do,” Marques says. “Using pesticides alone is not going to do it. You have very large areas that are densely populated, with poor urban planning. There are lots of issues about water supply and trash collection – all these things are deficient. You can’t just push the responsibility to the general public and say, ‘You’ve got Zika because you didn’t put away your trash.’ ”
When I asked Dr. Anne Schuchat, the CDC’s principal deputy director, how Puerto Rico, which is facing an enormous financial crisis, would go about mosquito abatement, she said: “Mosquito control is very difficult…We think it’s really important for people to protect themselves because we may not be as effective in mosquito control as we’d like.”
But Lawrence Gostin, a public health policy expert at Georgetown University, says somehow the resources must be found.
“It would be truly unforgivable if we let Puerto Rican women have deformed babies because we were asleep at the switch or didn’t provide the proactive interventions that we should,” Gostin said.
As the Zika problem grows, Gostin foresees growing pressure to place travel restrictions on people coming to the U.S. from affected areas.
“I can absolutely foresee that,” he said. “But you can’t interdict infected travelers. You simply can’t.”
For one thing, most people infected with Zika virus don’t have symptoms. And even among those who do, the symptoms mimic other diseases — and it’s not yet possible to do a quick test to distinguish a Zika infection from dengue or many other illnesses.
In any case, Gostin, an expert in public health law, says it would be unconstitutional to bar Puerto Ricans from entering the mainland, since they are American citizens.
Given the limited options for controlling Zika, it will be important to find out what kind of immunity people develop after they’ve been infected with the virus. If it’s strong and long-lasting, the pandemic might burn itself out as more and more people become immune. At this point the duration of Zika immunity is unknown.
If It Switches Mosquitoes
On the negative side of the ledger, public health experts worry that the Zika pandemic might become far worse if the virus adapts itself to infect another, closely related mosquito of the Aedes species — Aedes albopictus, the so-called Asian tiger mosquito.
“Tiger mosquitoes are larger, tougher insects that travel greater distances in their feeding compared to A. aegypti and can bite more people in a given day,” wrote Laurie Garrett of the Council for Foreign Relations in a blog post on Friday.
If Zika learns to hitchhike in tiger mosquitoes, its range would increase enormously, reaching deeper into North America during summers than A. aegypti does. It’s already present in about 30 states, including the entire eastern seaboard up to New York City.
More than 60 percent of the U.S. population lives in areas conducive to seasonal transmission of Zika if the virus were to adapt to transmission by both types of Aedes mosquitoes, according to an analysis published this month in The Lancet.
“The possibility that Zika may yet adapt to transmission by Aedes albopictus…is cause for concern,” Fauci and Morens write — with considerable understatement.