A World Gone Viral: Arboviral Emergence in Recent Decades

05/02/2023

A World Gone Viral: Arboviral Emergence in Recent DecadesA. Desiree LaBeaud, MD, MSStanford University

+What are Arboviruses? Arthropod-borne viruses Require a blood sucking arthropod to complete the life cycle

Often zoonotic At least 500 viruses Diverse: 8 viral families

• Togaviridae, Flaviviridae, and Bunyaviridae

+Arboviral Importance Every year, over 1 million people die from mosquito-

borne diseases• Children are at high risk

West Nile virus: widespread transmission of an ‘exotic’ pathogen and the substantial health impact

Recent introduction of more deadly arboviruses and their potential threat

Global distribution, limited by vector range

+

+Dramatic Resurgence Last 20 years: dramatic resurgence or emergence of epidemic arboviral diseases in humans and animals

Epidemics caused by arboviruses:• Thought to be under control:

‒ Dengue, yellow fever• Expanded geographic distribution:

‒ West Nile, Rift Valley fever, chikungunya

+Disease Emergence: Influences of Modern Life

UrbanizationDeforestation/Reforestation

Land Reclamation Irrigation ProjectsMilitary Activities/War

Natural Disasters

Extreme Weather Events

Climate Change

Reduced/Ineffective Vector Control

Increased Transportation

+Effects of Globalization Almost 2 billion people travel aboard commercial airlines every year

+Be a virus, See the world!

Gary Larson’s view of infectious diseases from FARSIDE

Man’sBlood

You are from Italy. Wow!!You have beautiful eyes….

Hey everyone, we are going to Rome!!!

+ Western Hemisphere Debut Flavivirus 1999: cluster of encephalitis was

reported in NYC Over the next 3 years WNV spread

• 2000: 21 cases; 3 states• 2001: 66 cases; 10 states• 2002: 4156 cases; 39 states

2003: largest NA arboviral epidemic• >9000 human cases and 100s of

deaths     Gubler CID

+WNV Human Cases 2015

05/02/2023

Dengue

Preparedness for the Zika Virus: A Public Health Emergency

Flavivirus400 million cases yearly

4 serotypesSpread by Aedes aegypti

Can be deadlyVaccine coming

05/02/2023Preparedness for the Zika Virus: A Public Health Emergency

+ Spread of Dengue in US Laredo, TX: 1999

• 50% exposed to dengue

Brownsville, TX: 2005• Autochthonous spread

• 38% seropositive

Key West, FL: 2009-2010• First cases outside TX since 1945

• Locally acquired

2013: South Texas, Florida• Long Island, NY

CDC. MMWR. Aug 2007.

+Chikungunya virus (CHIKV)

Togavirus, ssRNA positive-sense virus Transmitted by Aedes aegypti and Aedes albopictus

Causes a non-specific febrile illness Joint symptoms usually last weeks, but can last years

+Chikungunya Emergence

de Lamballerie X. Virology J. Feb 2008

+Spread into the Developed World

Chikungunya virus outbreaks: • 2004 Indian Ocean island/East Africa

• 2006 India

• 2007 Autochthonous spread in Italy

New vector: Aedes albopictus New virus: mutation in chikungunya

virus (A226V) improved virus survival in Aedes albopictus and also increased its virulence

Tsetsarkin KA. PLoS Pathogens. Dec 2007.

+CHIKUNGUNYA: 2013-Present

+CHIKV: Unwanted Souvenir At least 1 million cases of CHIKV have been confirmed in patients living in the Caribbean

First time that local transmission of CHIKV has been reported in the Americas • At least 1.6 million cases

9 million Americans travel to the Caribbean each year• CHIKV will be more frequent in the U.S.

+UNITED STATES of AMERICA

MEXICO

COLOMBIA

VENEZUELA

BRAZIL

PERU

BOLIVIA

HONDURAS

NICARAGUA

ECUADOR

GUYANA

SURINAME

FRENCHGUIANA

COSTA RICA

PANAMA

GUATEMALA

CUBA

PARAGUAY

ARGENTINA

URUGUAY

CHILE

GUYANASURINAME

FRENCH GUIANA

PANAMA

COSTA RICA

NICARAGUA

HONDURAS

GUATAMALAEL SALVADOR

BELIZE

Countries in the Americas where chikungunya cases have been reported: Mexico, Belize, Brazil, Colombia, Honduras, Costa Rica, Colombia, El Salvador, Ecuador,French Guiana, Guatemala, Guyana, Nicaragua, Panama, Paraguay, Suriname, Venezuela

Countries and territories in the Americas where chikungunya cases have been reported: Anguilla, Antigua and Barbuda, Aruba, Bahamas, Barbados, British Virgin Islands, Cayman Islands, Curacao, Dominica, Dominican Republic, Grenada, Guadeloupe, Haiti, Jamaica, Martinique, Montserrat, Puerto Rico, Saint Barthelemy, Saint Kitts and Nevis, Saint Lucia, Saint Martin, Saint Vincent and the Grenadines, Sint Maarten, Suriname, Trinidad and Tobago, Turks and Caicos Islands, US Virgin Islands

+Why does this keep happening? Global travel allows for imported cases Climate change allows for vector migration and adaptation Urbanization versus resource-limited regions

• Neglected diseases occur in neglected areas

Up to 5 million years of healthy life lost each year

LaBeaud et al., Pop Health Metrics 9:1, 2011

Early mortality and long-term, related chronic conditions worth more DALYsSeverely underestimated; Very little data

+Why are we constantly taken off guard?Disease outbreaks of never-heard-of organisms seem far awayReactive not proactive climate

• Funding• Media

Many scarier diseases• Rift Valley fever virus

+ PreventionAvoid exposure to mosquitoes

• Repellents: DEET and picaridin, permethrin• Wear long-sleeved shirts and long pants • Use air conditioners and/or window screens • Clean out standing water for source reduction

Abstain or practice safe sexNucleic acid screening of blood

+Behavior Change

+Conclusions Arboviruses are common in all parts of the world and are causing large outbreaks

Outbreaks devastate by both direct pathogen effects and bystander effects on food, shelter, and care

Co-circulation of dengue, chikungunya, and Zika is anticipated for the first time in the Americas

Small, local U.S. outbreaks of Zika likely to mirror DENV and CHIKV

More proactive approach is needed to combat continued arboviral emergence

+Thank you for your attention