By Rear Adm. Joyce Johnson, USPHS (Ret), D.O., M.A.
of early August, 1,825 cases of Zika virus had been reported in the
U.S., including 16 cases with documented sexual transmission. Of the
total reported U.S. cases, 1,818 were travel-associated cases, which
means they were linked to travel to areas with local mosquito
transmission; six cases were acquired from mosquito bites in the U.S.
(all in Florida); and one case was a laboratory worker. Additional cases
have been reported from U.S. territories - 5,460 locally acquired cases
in Puerto Rico, 44 in America Samoa, and 21 in the U.S. Virgin Islands.
All of these are reported cases and do not include the larger number of
asymptomatic unrecognized cases.
The routes of transmission of
the virus include mosquito bites, blood transfusions (though not
documented in the U.S.), from mother to unborn child, sexual
transmission, and laboratory exposure. Diagnosis remains a challenge
because no commercially available diagnostic tests have been cleared by
the Food and Drug Administration (FDA) for Zika virus. However, the FDA
has used its Emergency Use Authorization authorities to make several
assays available for clinical diagnosis. These are used on a regular
Symptoms, complications, and treatment
80 percent of those infected have no symptoms. Most of the 20 percent
who have symptoms have a very mild disease that might include some
combination of fever, rash, joint pain, and red eyes. Treatment is
supportive care - managing the symptoms.
The primary threat of
disease is to pregnant women because Zika is associated with the serious
birth defect microcephaly - in which the infant's brain does not
develop fully, with resulting lifelong intellectual and neurological
problems. This necessitates prevention in women who are pregnant or plan
to become pregnant. Preventing mosquito bites is key (see tips below),
as is preventing sexual transmission. Zika virus can be sexually
transmitted by people (male or female) who never get symptoms from the
infection; it also can be transmitted before symptoms begin, while
symptomatic, and after symptoms resolve. The virus can be transmitted in
semen for some weeks after infection. Preventing sexual exposure is
critical, especially in anyone who might become pregnant. Barriers, such
as condoms, are one way to minimize the risk of disease.
complication of Zika infection, though rare, is Guillain-Barre syndrome -
a neurologic disease in which the body's own immune system attacks
nerve cells and causes muscle weakness and sometimes paralysis and can
affect the muscles necessary for breathing. Of the 1,825 U.S. cases,
five also have had Guillain-Barre syndrome; of the 5,548 cases in U.S.
territories, 18 cases of Guillain-Barre syndrome have been reported.
Treatment requires aggressive supportive care, often in an intensive
care unit with a respirator to assist with breathing. With appropriate
care, the disease generally resolves over a few weeks to months, though
there might be some residual neurologic problems.
can be an effective way to prevent infectious disease. Though there are
no FDA-approved vaccines to prevent Zika virus infections, several
vaccines are under development.
Therefore, other prevention
methods are critical. Because the mosquito remains the primary route of
transmission, a field trial with genetically engineered mosquitoes is
being considered to see whether these mosquitoes will mate with local
mosquitoes and thus reduce the mosquito population. It currently is
making its way through the regulatory and approval processes.
is being done in the U.S. to protect the blood supply. Donations from
those at risk of infection are being deferred. Further, blood from the
U.S. is being provided to Puerto Rico because of the risk in potential
blood donors there. In the U.S., no cases of Zika virus infection have
been associated with blood transfusions.
Various public health
recommendations also are focused on preventing Zika infection. Many
communities are initiating aggressive programs to reduce mosquito
populations. Travel advisories are continuing in areas where
mosquito-borne Zika transmission is widespread.
Individuals should continue to take precautions to reduce mosquito bites, such as:
- avoiding mosquito-infested areas;
- eliminating stagnant water where mosquitoes breed;
FDA-registered insect repellents on skin as directed (but not under
clothing) or wear clothing impregnated with repellents;
- wearing long pants, long-sleeved shirts, and hats;
- tucking pants into boots, and avoiding sandals;
- staying in air-conditioned buildings and using window screens; and
- when camping, using a mosquito net.