New Invasive Mosquito Species Found in Pasadena

Posted on July 3, 2017 in

PASADENA, Calif.—Eggs from the Aedes albopictus mosquito that can infect humans with viruses such as Zika, dengue and chikungunya have been found in monitoring traps in Pasadena, the Pasadena Public Health Department (PPHD) announced today.  Health Officials emphasized there are no reported cases of locally transmitted Zika or the other two viruses by this type of mosquito in Pasadena.

“It is important for the public to be aware of the presence of this mosquito, which is different than the local variety of the insect, and to take steps now to help protect yourself and your family against these mosquitoes,” PPHD Health Officer Dr. Ying-Ying Goh said.  “We are asking for the public’s help to take immediate action now in preventing the spread of this mosquito, such as eliminating all standing water sources on their property.”

More than a dozen mosquito egg traps have been placed throughout Pasadena by the San Gabriel Valley Mosquito and Vector Control District (SGVMVCD) and four traps tested positive for eggs indicating that the Aedes albopictus mosquitoes, commonly called the Asian tiger mosquito, are now in Pasadena.  Positive identification was confirmed on June 21, 2017, marking the first time that the small, daytime-biting mosquito has been detected in Pasadena.

The SGVMVCD will be routinely testing mosquito samples found in Pasadena and throughout the District for those viruses.  Again, to date, no Aedes mosquitoes carrying any of these viruses have been detected in Pasadena, Dr. Goh said.

Since 2016, there has been only one travel-associated case of laboratory-confirmed Zika virus infection in the City of Pasadena, and no cases of locally-acquired Zika reported to PPHD.  As of June 30, 2017, there have been 573 such travel-associated Zika virus infections throughout all of California, but no cases of locally-acquired Zika anywhere in the state, according to the California Department of Public Health,

There also have been no West Nile Virus infections in Pasadena reported to PPHD so far in 2017.

For more information about the Aedes mosquito or to report possible sightings, contact the SGVMVCD at (626) 814-9466, or online at  The attached flier also has additional information.

The invasive, non-native Aedes mosquitoes have been present in Southern California since about 2001, including other parts of the San Gabriel Valley and include three different species.  The eggs found in Pasadena so far indicate the presence of only Aedes albopictus.  The mosquito is roughly half the size of the more common mosquito.  It bites primarily during daytime hours, not when other mosquitoes normally are active at dusk or dawn, and it will repeatedly bite a person.

Health and vector control officials plan to increase surveillance and initiate localized treatment where breeding is occurring.  Clearly identified vector control officials also will be going door-to-door to help educate the public and take appropriate action.  Currently, no widespread spraying is required.

Since the beginning of this year, PPHD has been working with SGVMVCD to annex the City into the District’s service area for mosquito and vector control services.  Full merger should begin in 2018.  In the interim, the City and SGVMVCD in late June signed a memorandum of understanding authorizing SGVMCD to conduct Aedes mosquito surveillance, investigation, control and abatement, and public outreach about protection and prevention in Pasadena.

“Our best defense is education and prevention,” PPHD Director Michael Johnson said.  “Direct application of a treatment can occur where active breeding is happening, but people really need to be proactive to eliminate even the smallest amount of standing water to prevent possible breeding.”

Aedes mosquito larvae can successfully mature to become adult mosquitoes in containers with as little as a bottle cap full of water, which is why PPHD is urging everybody to have increased vigilance in eliminating all sources of mosquito breeding environments on their properties, Dr. Goh said.

Additional action steps to take to fight against all types of mosquitoes include:

  • Empty, scrub clean with hot water, turn over, cover–or throw out–unused outdoor items that hold water, such as tires, buckets, planters, toys, pools, birdbaths or flowerpots.
  • Keep swimming pool water clean, sanitized and filtered. Same with ponds or birdbaths.
  • Wear insect repellants containing DEET when outdoors.
  • Wear long-sleeved shirts and long pants when outdoors if weather permits.
  • Check window and door screens for holes, repair or replace.
  • When traveling, choose lodging that has air conditioning and screens.

The U.S. Centers for Disease Control and Prevention recommends that pregnant women (or women considering getting pregnant) should avoid travel to areas with ongoing Zika virus transmission, including Latin America and the Caribbean, particularly Mexico and Puerto Rico. For more on the CDC’s travel advisories, please visit

Zika virus was first identified in the 1950s as a tropical disease transmitted by mosquito bites.  It became a more pronounced health issue in South America, including negative birth defects, in 2015.  People who contract mosquito-borne viruses may not have obvious symptoms.  It is possible that people who have the Zika virus can infect others through sexual transmission or by mother-to-child transmission.  Aedes mosquitoes also can become infected with the virus if they bite an infected person while they still have the virus in their blood.

For 125 years, the PPHD has worked to promote and protect the health of the greater Pasadena area.  The department is nationally accredited by the Public Health Accreditation Board.

The San Gabriel Valley Mosquito and Vector Control District was formed in 1989 to protect residents against vector-borne diseases.  The District provides enhanced mosquito and vector control services to 23 cities and portions of unincorporated Los Angeles County within the San Gabriel Valley.  For more information, call (626) 814-9466, visit and follow on Facebook and Twitter @SGVMosquito.

Stay connected to the City of Pasadena!  Visit us online at; follow us on Twitter @PasadenaGov,, and Instagram @PasadenaGov,; on Facebook at; and subscribe to our YouTube channel at  Watch live streaming or archived video on demand about us on KPAS, the City’s government cable TV channel, at  Or call the Citizen Service Center, , 7:30 a.m. to 5 p.m., Monday through Friday at (626) 744-7311.

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FOR IMMEDIATE RELEASE:  July 3, 2017  #034-17

NEWS MEDIA CONTACTS:  William H. Boyer, Pasadena Public Information Officer, City Manager’s Office, (626) 744-4755,  OR  Jason Farned, Public Information Officer, San Gabriel Valley Mosquito & Vector Control District, (626) 814-9466,