Chikungunya

USAF School of Aerospace Medicine

Background• Chikungunya:• Viral disease (Genus Alphavirus; Family Togaviridae)• Transmitted by mosquitoes (Genus Aedes)• Symptoms are often severe and debilitating• Fatalities are rare• Past infection gives long lasting immunity

• At risk individuals:• Anyone who has not previously been infected by the virus• Outbreak attack rates of 38%-63%

Disease Distribution• First outbreak in the Americas (2013)

• Islands in the Caribbean began reporting local cases

• Previous outbreaks in:• Africa, Asia, Europe, and islands in the Indian and Pacific Oceans

• Risk of outbreaks occurring in the U.S.• Vectors are present in various areas within the U.S. and its territories

• Dengue and chikungunya viruses • Transmitted by the same mosquitoes• May circulate in the same area• Co-infections are possible

• For an up-to-date map of countries and territories where outbreaks have occurred visit: http://www.cdc.gov/chikungunya/geo/index.html

• Predicted range of chikungunya vectors by country (based on CDC, WHO, ECDC data)

• States and territories with chikungunya vector populations

Clinical Findings• Incubation period:

• 3 to 7 days• Acute phase:

• 3 to 10 days• Main signs and symptoms:

• Fever >102.5°F (39°C)• Severe pain in multiple joints

• Other common signs and symptoms include:• Headache• Rash• Muscle pain• Nausea/vomiting• Conjunctivitis

• Relapse of rheumatic symptoms may occur• Most common 2-3 months after initial infection• Patient is no longer viremic

• Chronic chikungunya• Symptoms lasting for more than 3 months (absent viremia)

• 72% to 97% of infected individuals will become symptomatic.

Case Reporting• Chikungunya infection should be considered if:• Symptoms include acute onset of fever with severe pain in

multiple joints AND• The patient lives or has recently traveled to areas where

chikungunya outbreaks occur• Public Health Flight should report suspected cases to:• Local/county/state/territory health departments• The Air Force (via AFDRSi) under “Any Other Unusual Condition

Not Listed”

Treatment• No antiviral therapy exists.• Supportive care

• Rest• Fluids• Acetominophen, paracetomol, or non-

steroidal anti-inflammatory drugs (NSAIDs) may be used to reduce pain and fever

• Aspirin is NOT recommended due to the possibility of bleeding in some patients

• NSAIDs should NOT be used if there is a possibility the patient has dengue

Transmission• Main mode of transmission:• Via the bite of an infected mosquito

• Aedes aegypti (yellow fever mosquito)• Aedes albopictus (Asian tiger mosquito)

• Less common modes of transmission:• Mother to fetus • Via infected blood• (No evidence of transmission via breast milk)

• To reduce local transmission rates: • Infected individuals should avoid mosquito contact during the first week of illness. Image courtesy of AFPMB Technical Guide No. 47

The Vectors• Aedes aegypti and Aedes albopictus• Small, black and white mosquitoes• Breed in containers

• Aquatic cycle (from egg to adult) may be completed in

as little as 7 to 9 days.• Bite during the day

• Peak feeding times in the early morning and before dusk

• Same mosquitoes that transmit dengue

Aedes aegypti• Guitar or lyre-shaped markings

on the thorax

Prevention• No vaccine or medication can prevent chikungunya infection.• Avoid mosquito contact!• Use insect repellent such as DEET or picaridin on exposed skin.• Wear uniform or long-sleeved shirts and long pants.• Treat clothing or uniform with permethrin repellent.• Use air conditioning. • Ensure window/door screens are tightly sealed and intact. • Reduce mosquito breeding sites

• Empty or remove containers around the home or base that collect standing water.

Vector Surveillance and Reporting• Larval surveillance of containers that hold water

for more than a few days. • Determines the number, type, and distribution of

containers producing chikungunya vectors• USAFSAM/PHR is able to test known chikungunya

vectors for the virus. • Positive mosquito pools should be reported to

local/county/state/territory health departments.

Vector Control• Source reduction:• Focuses on containers that hold water and serve as larval habitats.• Helps to reduce mosquito density.

• Larval control:• Larvicides (chemical and biological) applied to potential larval habitats

• Adult mosquito control:• Early morning or late evening ultra-low volume (ULV) applications

For more information• CDC/Chikungunya

• PAHO

• CDC/PAHO Preparedness and Response for Chikungunya

Virus Introduction in the Americas

• Armed Forces Pest Management Board

• AFPMB Dengue and Chikungunya Vector Control Pocket Guide• USAF

Guide to Operational Surveillance of Medically Important Vectors and Pests• https://gumbo2.wpafb.af.mil/epi-consult/entomology

Presentation Prepared by Jamie Iten