Nevada State Epidemiologist's Zika Presentation

Overview of the Emerging

Zika Virus (ZIKV) Challenge

Nature of the Threat:

• Vector-borne via mosquitos
• Arbovirus, Flavivirus
• Humans act as the "principal amplyfying host during outbreaks" (CDC's MMWR for 2/19/16)
• "Infection is usually asymptomatic"
• Symptoms: generally mild,
• Fever
• Rash
• Arthralgia (aka: joint pain)
• Conjunctivitis (aka: red eyes)
• Differential Diagnosis:

"Zika's long, strange trip into the limelight"

Science Magazine

Jon Cohen

February 8, 2016

How did ZIKV go from a 'virological curiosity'

to a WHO-identified

"Public Health Emergency of International Concern"?

First isolated from a rhesus monkey in 1947.

Who: Approx. 7,000 citizens

What: Asian lineage

• 73% of residents aged >3= years had recently been infected
• 18% had clinical illness
• 185 cases (26% confirmed, 32% probable)

Where: Federated States of Micronesia in the western Pacific, Yap Island, in 9 out of 10 municipalities

When: April 2007 through July 2007

Why: Possibly introduced through a viremic human traveler from the Philippines

How: Vector primarily identified was A. hensilli mosquito

Who: 28,000 sought medical care (symptomatic)

• The 1:4 Ratio Rule-of-Thumb
• If 80% had no symptoms, then as many as 140,000 were infected
• This represents 51% of the population

What: Asian lineage

• Largest ZIKV outbreak recorded
• Related to virus involved on Yap Island
• Complications: neurological such as GBS, and physical such as microcephaly
• Co-circulation w/ another arbovirus: Dengue

Where: French Polynesia

When: October 2013 through May 2014

Why: Most likely introduced through viremic human travelers

How: Vector primarily identified was A. aegypti mosquito, with A. polynesiensis also playing a role.

• Intensely researched outbreak

Import to Brazil:

• Original Hypothesis:
• Football World Cup: June/July 2014
• Aquece Rio International Canoe Sprint: Sept. 2014
• Current Science:
• N.R. Faria et al., Science 10.1126/science.aaf5036 (2016)
• "Zika virus in the Americas: Early epidemiological and genetic findings"
• "We estimate that the date of the most recent common ancestor of all Brazillian genomes is August 2013 to April 2014."

Who: As of March 2016

• Approximatley 1.5+ million infected

What: Asian lineage

• Over 30,000 cases
• Microcephaly: Brazil went from <200/year to nearly 5,000
• Guillain-Barre Syndrome (GBS): Over 1,700 and rising
• Rare disorder, immune system attacks nerves, muscle weakness, motor coordination issues, paralysis
• Can last days/weeks/months

Where: Brazil (widespread local transmission)

• Began in northeastern states, then quickly spread to 22 of Brazil's 27 states

When: May 2015 through December 2015, with epidemic peak in mid-July 2015

Why: Most likely introduced through viremic human travelers

How: Vector primarily identified is A. aegypti mosquito, and A. albopictus mosquito

Modes of Transmission:

• Mosquito bites
• Mother to Child
• Sexual Contact
• Blood Transfusion

Travel-associated versus

Locally acquired

We have already seen a few travel-associated human cases of ZIKV here in Nevada, and will continue to see more.

CDC's Division of Vector-Borne Diseases (DVBD):

• Fort Collins, CO
• Remember: Up until 2007 there were only 14 human cases and no reported outbreaks:
• Science needs to catch-up:
• Correlation of microcephaly
• Correlation of GBS
• New vectors / new reservoirs
• Incubation period
• Survivor transmissibility
• Sexual transmission
• Interplay of Dengue/Chikungunya antibodies with ZIKV
• Insecticide involvement

1) Mosquitos in Nevada:

• Season is May to October
• In 2014 there were eleven different Aedes species in NV
• In 2015 there were nine Aedes species

Frequently Asked Questions

(FAQs)

ZIKV Vectors

A. aegypti:

• Brown and white
• Violin shape
• Daytime biter
• Bites multiple people in one feeding
• Rests indoors

A. albopictus:

• Black and white
• Aka: Asian Tiger
• White stripe down back
• Leg stripes/bands
• Daytime biter
• More common in N. America

Zika's Origins and Eastward Migration:

1947 to 2006

Zika in the Pacific:

2007 to 2014

1954: Nigeria

In spite of this eastward migration over 60 years, up to 2007 there were only 14 documented cases of ZIKV illness in humans, and no reported outbreaks.

Zika's Arrival to the Americas: 2014-2015

Two Lineages: African and Asian

French Polynesia