By the end of this week, all blood banks in the
continental United States must begin testing donated blood for contamination
with the Zika virus. Many banks are doing so already, and the early
results indicate that the country has dodged a bullet — for now.
Screenings in a dozen states suggest that Zika
infection remains exceedingly rare. Among the approximately 800,000 blood
donations tested in the past six months or so, about 40 were initially positive
for the virus.
“It is good news that we are avoiding the transmission
of Zika,” said Dr. Susan Rossmann, the chief medical officer at Gulf Coast
Regional Blood Center in Houston.
Still, she noted, it may not be surprising there are
so few possibly positive cases, because blood banks have been dissuading people
from donating if they recently traveled to an area in which the virus is
circulating.
Blood donation screening for Zika is performed with
tests made by Roche
Molecular Systems or
by a collaboration between two medical companies, Hologic Inc. and Grifols.
The screening effort is regulated as two gigantic
clinical trials in which every blood donor is enrolled as a participant. All
the results, therefore, are reported to the companies.
By Friday, Roche’s machines had screened 475,000
donations in the United States, excluding Puerto Rico. Just 25 have been
“initially reactive” for Zika infection, said Tony Hardiman, who leads the
company’s blood screening program.
“Compared to Puerto Rico, it’s tiny,” he said.
Roughly 1 percent of the blood donors in Puerto Rico
were infected by July, with 1.8 percent of them testing initially positive in
the last week of surveillance, according to the Centers for Disease Control and Prevention.
By mid-October, roughly 348,000 donations had been
screened using the test made by Hologic Inc. and Grifols. Fourteen were
initially positive for the Zika virus.
It may be that not all of these samples are truly
contaminated. The technology is still in development, and the manufacturers are
scrambling to confirm their results with further investigations of the donors.
Of three donors examined by Hologic and Grifols, all
seem to have been infected outside the United States. One donor gave blood at
United Blood Services in Reno, Nev., after visiting Nicaragua. Another, a New
Yorker, had been to Trinidad. The third lives in Arizona and had visited
Mexico.
All three donors had minute traces of the Zika virus in
their blood, detected between 41 and 97 days after travel abroad, Jeffrey
Linnen, an associate vice president at Hologic, told attendees at a recent
conference for AABB, the standards-setting group for most blood banks
nationwide.
Viral material detected after 40 days is unlikely to be
live virus, said Dr. David O. Freedman, an infectious disease specialist at the
University of Alabama at Birmingham.
“The farther along you are after infection, the more
likely you are just detecting residual breakdown products from dead virus
pieces that are still circulating,” he said.
In August, the Food and Drug Administration
required all blood banks to
screen each of the millions of blood donations collected annually for Zika.
Eleven states in high-risk areas had to put in the new safeguards in a month.
The rest must do so by Friday.
At the time, experts feared that Zika-infected
mosquitoes would begin turning up in states along the Gulf Coast, prompting
outbreaks like those seen in South America and threatening the nation’s supply
of donated blood.
Universal screening was necessary to avoid
transmission of the Zika virus in donated blood, particularly to pregnant
women. If exposed to the virus in utero, fetuses can have brain damage, visual
and joint problems, and muscle tone so rigid it restricts movement.
Florida is the only state with documented local
transmission of the virus. In July, the F.D.A. temporarily halted collection of
blood donations in Miami-Dade and Broward Counties until screening for the Zika
virus could be put in place.
Blood banks perform the screenings themselves or, more
often, pay a laboratory to insure donations are Zika-free. The additional costs
are passed on to hospitals.
The range is from $6 to $10 a unit, Dr. Rossmann said.
“It’s not inconsiderable, that’s for sure.”
One 2011 survey found that hospitals paid $210 on average for a unit of
red blood cells,
after screening for pathogens. The cost of blood is increasing, the researchers
also concluded.
“The F.D.A. requirement made it pretty clear that we
don’t have much of a choice, and the hospitals don’t have much of a choice,”
Dr. Rossmann said.
Meeting the deadlines has been a monumental task for
blood banks. Introducing a new test to screen donations usually takes six to 12
months.
The F.D.A.’s timeline was just one month for blood
banks in Florida and 11 other states thought to be at high risk for Zika
outbreaks, and three months for those in 38 other states.
“It was extremely painful, extremely expensive,” said
Phillip Williamson, the vice president for operations and scientific affairs at
Creative Testing Solutions. “This was an unfunded mandate from our government.”
Rhode Island
Blood Center, for
example, acquired two new machines to screen 153,000 annual donations and
trained 17 employees to load blood samples and run the automated testing around
the clock.
“We’ve been scrambling to get ready,” said Dr. Carolyn
Young, the chief medical officer.
In the coming months, the main threat to the blood
supply will be the roughly 4,000 travelers infected with the Zika virus while
abroad. Most do not have symptoms.
Dr. Lyle Petersen, the director of the division of
vector-borne diseases at the C.D.C., has called the number of travel cases in
the continental states “extraordinary.”
The fear is not that they will all seek to donate
blood, but that they will serve as vectors by which the Zika virus will spread
in the population, even when the mosquitoes that carry the infection are not
present.
Sexual transmission is the likeliest route. “When
people come back from trips, they generally have sex pretty soon,” Dr. Petersen
recently told a packed room at an annual conference for blood transfusion
experts.
In all cases the C.D.C. has studied, he said,
“transmission from infected travelers to their nontraveler partners has
occurred within 20 days of the first sexual contact.”
Recently infected travelers have higher levels of Zika in their blood, semen and
other bodily fluids, and are probably more infectious.
Blood banks had been asking donors about their travel
history and that of their sexual partners, and then asking them to postpone
donating for at least a month.
To prove that their new tests work reliably enough to
be licensed, Hologic, Grifols and Roche may need to enroll millions of
participants in their continuing trials.
Roughly seven million people give blood
annually; Creative Testing Solutionsscreens about a third of them. “We have to sign up
every one of those people for a clinical trial,” Dr. Williamson said.
While the nonprofit can handle the burden, he added,
“I’m sure a lot of places out there are struggling as the result of the
aggressive implementation guidelines mandated by F.D.A.”
Still, most experts agree that universal screening is
costly but necessary if the country wishes to avoid even a single instance in which
a child is brain-damaged because of a transfusion of contaminated blood.
The Community Blood Bank of Northwest
Pennsylvania and Western New York, based in Erie, Pa., has been drawing extra tubes of
blood from donors to fly overnight to a Houston laboratory for Zika screening
at $6 to $10 a sample.
“Compared to the overall cost of health care,” said
Scott Greenwell, the executive director of the blood bank, “this is spit in the
ocean.”
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