On Thursday, Centers for Disease Control and Prevention (CDC) Director, Dr Thomas Frieden addressed the National Press Club on Zika virus and the response efforts being taken.

During his talk, Frieden, who called Zika “unprecedented and tragic”, listed 10 things that have been learned in the past five months:

Thomas Frieden/CDC
Thomas Frieden/CDC

First, it is an extraordinarily complex response.  In fact, of all the responses I have overseen, it’s probably the most complex.  We have involved almost every single part of CDC.  We’ve had more than a thousand of our staff involved.  Whether it’s mosquito control or virology or sexual transmission or obstetrics or newborn care, many, many parts of our agency are fully activated to support the response.

Second, it’s now clear that Zika causes microcephaly and other birth defects.  I vividly remember sitting with Dr. Zaki, our chief infectious disease pathologist, and having him show me the very special stains that he had done to show that Zika virus actually invading the neural tissue of newborn infants and destroying it.  This is a horrible thing to see.  It is just the kind of thing you would never want to see.  And yet to understand that when a child is born with microcephaly, it’s not because the skull was malformed.  It’s because the virus destroyed the brain cells.  And the skull collapsed around the demolished or devastated brain.  It’s a horrible situation.

Third, we have now seen clear evidence that even asymptomatic infection with Zika during pregnancy can result in microcephaly.  And we know from past studies, about four out of five Zika infections appear to be asymptomatic.

Four, Zika almost certainly causes Guillain-Barre syndrome.  This is temporary paralysis.  This isn’t so surprising.  We’ve seen it with other infections.  It is generally treatable.  That’s not what’s so unusual about Zika.  What’s so unusual about Zika is the threat to pregnant women.

Five, diagnosing Zika is hard.  But we’ve made enormous progress.  CDC laboratory scientists have optimized testing so we now have a rapid, highly sensitive test that can be used in urine or blood that can pretty accurately detect the virus in someone who is acutely infected.  We’ve disseminated them to a hundred labs around the U.S. and in countries around the world.  We’ve also improved the CDC mac-ELISA. It’s not perfect but it’s the best test out there.  As well as a more rapid test or a more complex test to try to determine which of several similar infections the person may have had.  It’s a neutralization assay.  We’ve provided more than a million of those tests.  So testing is hard, but we’re making progress.

Six, controlling this mosquito is really hardAedes aegypti is the cockroach of mosquitoes.  It lives indoors and outdoors.  It bites during the daytime and the nighttime.  Its eggs can last for more than a year.  They can hatch in a drop of water.  In parts of the U.S. and Puerto Rico, they’re highly resistant to certain insecticides.  They prefer people, so they generally spread disease among people.  And when they take a blood meal, they’ll often bite four or five people at once.  So they’re capable of rapidly spreading the infection.  There is no example of effective control of this mosquito in the modern era.  I vividly remember in a trip to Puerto Rico, our lab team had set up a laboratory that hatched mosquitoes.  And they were testing them for resistance.  We put them in a bottle coated with insecticide to see whether they’re knocked down or not.  And to see them in a bottle that had been coated with what should be a very effective insecticide happily flying around minute after minute, hour after hour, shows us how important it is that we improve the methods we have of controlling mosquitoes.

Seventh, there are also other routes of transmission.  We did not expect that sexual transmission would be as common as we’ve seen it.  We’ve had 10 documented cases in the U.S.  We’ve never had sexual transmission of dengue or West Nile, but Zika can spread sexually.  That adds a new level of risk and a new message that if your partner is pregnant, and you’ve been in an area with Zika, use a condom.  Also blood safety.  Theoretically it’s possible that there could be transfusion-associated Zika.  That’s why we’re so grateful for Roche and the FDA, they’ve come out with a terrific, highly sensitive test already being used in Puerto Rico to screen the blood supply.

Eighth, Puerto Rico has a particular challenge.  They were dealt a bad hand by nature when it comes to mosquito-borne disease.  And we need to do everything we can to reduce risk there.  The risk is still to pregnant women; it’s not a broader risk.  But it is an enormous challenge in Puerto Rico.  We’re continuing to see women infected with Zika in Puerto Rico and we are very concerned about what the coming months will hold.

Ninth, the role of globalization and urbanization is crucial.  We have at least 40 million visits from the U.S. to places around the world where Zika is spreading.  We’re not going to stop the world because we want to get off.  Globalization and global travel has a lot of benefits in economic productivity, in interchange among people, in the ability to do what we do in the world.  But it does also have the inevitability of bringing risks closer to home.  A disease threat anywhere in the world may be just a plane ride away.  And the greater urbanization of the world is also facilitating outbreaks of Yellow Fever, in the Ebola epidemic.  It was the first time we had seen urban spread of Ebola which was enormously challenging to control.

Finally, I would like to say a word, tenth, about the remarkable innovations going on through CDC scientists, doctors, and other researchers.  We think of CDC as working with boots on the ground to protect you, and we are that.  We’ve also developed cutting edge technologies, virus-like particles and chimeric solutions that can knock down the spread of diseases spread like Zika by half, very simply, at a low cost.  And now we’re going to see if that can be implemented on a broad scale.  We’ve been working many years on a new class of insecticide that appears to be nontoxic, food grade, smells a little bit like grapefruit, and may be as effective as DEET.

Watch the speech below: