Alameda County Public Health Official and Washington Hospital Infectious
Disease Specialist Note that Zika Cases in California are all Associated
with Travel Outside the U.S.
“While the Zika virus has become a public health issue of international
concern, the risk for contracting Zika virus disease in Alameda County
remains very low,” says Erica Pan, MD, MPH, FAAP. Dr. Pan is the
director of the Division of Communicable Disease Control and Prevention
and deputy health officer of the Alameda County Public Health Department.
Zika virus was first discovered in 1947 and is named after the Zika forest
in Uganda. Zika virus disease is spread primarily by Aedes aegypti mosquitoes
(also known as yellow fever mosquitoes) or Aedes albopictus mosquitoes
(also known as Asian tiger mosquitoes) that are infected with Zika virus.
These are the same mosquitoes that spread dengue and chikungunya viruses.
Zika virus is not spread through casual contact such as touching or hugging
an infected person, but the Centers for Disease Control and Prevention
(CDC) has cited evidence that men can spread Zika virus to their sex partners.
“So far, all of the confirmed cases of Zika in California have been
related to travel outside the United States,” Dr. Pan notes. “The
Zika virus is much more common in tropical and subtropical areas in Africa,
Southeast Asia and various islands in the Pacific Ocean. Recent outbreaks
of Zika in the Caribbean and in Central and South America have increased
the concern about the disease, particularly because there is a possible
association between Zika and potential birth defects, including microcephaly
– an abnormally small head and brain. More studies are needed to
evaluate this potential relationship between Zika and microcephaly and
other adverse fetal and infant outcomes.”
As of March 23, 2016, the CDC reported 273 cases of Zika in the United
States, none of which were acquired via mosquito bites in the U.S. Of
those cases, 19 are pregnant women, and six of the cases were sexually
The California Department of Public Health (CDPH) reports that as of March
25, there have been 22 cases of people in California with confirmed diagnoses
of Zika virus disease in 2015 and 2016. All of the cases have been travel-associated,
according to the CDPH. The majority of the cases (14) have been in southern
California counties. In northern California, there were three cases in
Contra Costa County, one case in Alameda County, one case in Napa County,
one in San Francisco, one in San Joaquin County and one in Yolo County.
One case in San Diego reportedly is a woman who was infected via sexual
contact with an infected partner who returned from traveling in the South
American country of Colombia. The case in Napa County is a pregnant woman
who contracted the virus while traveling in Central America.
“The number of confirmed cases in California is expected to increase
as people become more aware of Zika and seek testing,” Dr. Pan says.
“Zika is actually a very mild disease for adults, and only about
20 percent of people with Zika will have any symptoms. Our main concern
is for pregnant women or women who want to become pregnant because of
the potential risks to the fetus.”
The CDC reports that the most common symptoms of Zika include fever, rash,
joint pain and conjunctivitis (red eyes). In most known cases of likely
sexual transmission, the men had Zika symptoms, but the virus can be transmitted
before, during and after symptoms develop. The virus remains present in
semen longer than in blood.
“Aedes mosquitoes have been found in 12 California counties, mostly
in the southern part of the state and the Central Valley,” says
Dianne Martin, MD, an infectious disease specialist and co-chair of the
Infection Prevention and Control Committee at Washington Hospital. “Fortunately,
here in the Bay Area, we do not have the climate for these types of mosquitoes
to thrive because of our cooler weather. Nevertheless, it makes sense
to take steps to avoid mosquito bites, especially because West Nile virus
– which also is transmitted by infected mosquitoes – is still
a concern in the Bay Area.”
CDPH recommendations for protecting yourself from mosquito bites include:
- Use insect repellents containing DEET, picaridin, IR3535, oil of lemon
eucalyptus, or para-menthane-diol for long-lasting protection
- If you use both sunscreen and insect repellent, apply the sunscreen first
and then the repellent • Pregnant women and women who are breastfeeding
can and should choose an EPA-registered insect repellent and use it according
to the product label
- Wear long-sleeved shirts and long pants
- Use air conditioning or window/door screens to keep mosquitoes outside
- If you are not able to protect yourself from mosquitoes inside your home
or hotel, sleep under a mosquito bed net
- Help reduce the number of mosquitoes outside by emptying standing water
from containers such as flowerpots or buckets
According to the CDC, most mosquitoes bite in the early evenings or near
dawn, but Zika-carrying mosquitoes bite mostly during the day. In addition,
these mosquitoes do not breed out in the open near ponds, lakes or wetlands
like most mosquitoes. Instead, they are “city-slickers” that
prefer to breed in manufactured containers such as birdbaths, buckets,
barrels, kiddie pools and old tires.
In addition to avoiding mosquito bites, Dr. Martin recommends restricting
your travel to areas where the Zika virus is spreading rapidly, if possible.
“If you have traveled to areas where Zika virus is common, such as
Brazil, Puerto Rico, the U.S. Virgin Islands and American Samoa –
especially if you are pregnant – you should ask your doctor whether
you should be tested for the virus,” she emphasizes. “Men
who have traveled to those locations and have experienced Zika symptoms
also should be tested if they have female partners who are pregnant or
intend to become pregnant. We really don’t know yet how long the
virus remains in the blood, but most sources say about 28 days.”
Previously, blood tests for Zika had to be sent to the CDC for processing,
and it could take two to three weeks to get results. As of March 11, however,
the CDPH lab in Richmond has been authorized to process Zika tests, producing
results more quickly for residents of the Bay Area. A physician referral
is required for testing, and currently all testing is routed and approved
through local public health departments.
“Microcephaly is a rather nonspecific condition, and it could be
due to a variety of causes,” says Dr. Pan, who is also a pediatric
infectious disease specialist. “There is increasing evidence, however,
that points to the Zika virus being a potential cause of microcephaly
and other problems for the fetus throughout gestation. A recently released
report on nine pregnant travelers who acquired Zika showed that two of
them had early miscarriages, and three had babies born with microcephaly.
Obviously, there is increasing evidence for concern, and further study
Dr. Martin echoes the concerns expressed by Dr. Pan.
“We do know that Zika virus can be present in semen longer than in
blood, but we do not know how long the virus is present in the semen of
men who have had Zika,” says Dr. Martin. “Therefore, out of
an abundance of caution, the CDC recommends avoiding pregnancy and to
abstain from sex or use condoms during sex for at least six months after
the onset of symptoms if the man has tested positive for Zika to help
avoid transmitting the Zika virus to female partners. In addition, if
the man’s partner is a pregnant woman, he should use condoms consistently
and correctly or abstain from sex for the duration of the pregnancy.”
For more information about the Zika virus from the Centers for Disease
Control and Prevention, visit www.cdc.gov/zika/index.html.
Information about the Zika virus from the California Department of Public
Health is available at www.cdph.ca.gov/HealthInfo/discond/Pages/Zika.aspx.
The CDPH updates its report on the number of laboratory-confirmed positive
Zika cases in California every Friday.