Editor’s Note: Last week, the Massachusetts Department of Public Health posted new clinical guidance for physicians about the Zika virus on its website, which also includes handouts in multiple languages about the virus and travel advice for patients.
MMS spoke with Catherine Brown, D.V.M., M.S., M.P.H., Deputy State Epidemiologist and State Public Health Veterinarian at the Massachusetts Department of Public Health, about the potential for contracting Zika in the Commonwealth and what physicians and patients need to know.
We’ve seen a lot in the news about the Zika virus.
Should we be concerned about Zika virus in Massachusetts?
It’s extremely unlikely that we’ll see mosquito-borne Zika virus in Massachusetts. The conditions in Massachusetts are not conducive to mosquito transmission of the virus here. In order for the Zika virus to spread, there needs to be widespread established populations of mosquitos and a significant number of people actively infected with that widespread population of mosquitoes.
Dr. Catherine Brown, Massachusetts Department of Public Health
The primary vector of Zika virus, not just in this current outbreak, and in almost all outbreaks, has been the yellow fever mosquito Aedes aegypti. This mosquito is more likely to spread disease because it breeds successfully in urban environments, and bites, almost exclusively, people–it doesn’t feed on other mammals—and unlike other types of mosquito, it takes multiple blood meals. Most mosquitoes take a single blood meal, so are less likely to transmit disease. The Aedes aegypti mosquito has not been found in Massachusetts.
The secondary vector is the Asian tiger mosquito Aedes albopictus. This is a non-native introduced species that is well established in the southern tier of the U.S. It feeds on humans as well as other mammals. There is some evidence, from Massachusetts mosquito surveillance, that we have geographically isolated and sporadic findings of Aedes albopictus. However, as with Aedes aegypti, there would need to be widespread established populations as well as significant numbers of actively infected people in contact with that widespread population of mosquitoes in order to spread the virus. The people in Massachusetts who have been infected with the virus are travelers returning from affected areas; they don’t carry the virus in their blood for very long.
So the risk for people in Massachusetts relates to those traveling to or from an affected region. What regions in and out of the U.S. are affected?
As of [this interview], there have been no cases of locally acquired, mosquito-borne transmission anywhere in the United States. The areas involved in the current epidemic of Zika virus are most of Central and South America and the Caribbean, as well as Cape Verde and Papua New Guinea. The U.S. Territory of Puerto Rico has been particularly hard hit. This is the largest outbreak of Zika virus ever documented, both in terms of number of people infected and the geographic range of the outbreak. Because infection with Zika virus likely confers long-term immunity, previous outbreaks have waned relatively quickly as the percentage of susceptible people in the population declines.
Travelers concerned about the status of the Zika virus should check the CDC website for the most updated information on currently affected areas.
What are the symptoms of Zika?
Eighty percent of people infected with Zika virus will never develop symptoms. For those that do become symptomatic, the most common complaints are fever, a rash, joint pain and non-purulent conjunctivitis. Headache and pain behind the eyes have also been reported. For the vast majority of people, the illness lasts between two to seven days and is self-limiting. No specific treatment exists. Hospitalizations associated with Zika virus infection are rare but have been associated with Guillain-Barré, meningoencephalitis, and other neurologic problems.
It is not known if there are particular groups of people that are more likely to develop disease, or who are more likely to develop severe disease, including Guillain-Barré. No evidence exists that pregnant women, infants, or children are at greater risk for developing disease and information about risk in immune-compromised patients is limited.
What is the risk from Zika to humans?
The most significant concern from Zika virus infection is for pregnant women who can transmit the virus to a developing fetus.
Right now, there are still more questions than answers about Zika virus. We do know that women infected with Zika virus during pregnancy are more likely to give birth to an infant with birth defects or some other poor birth outcome. Exactly how much risk is associated with infection is not known. There is some information that infection with Zika virus during the first trimester, as opposed to later trimesters, is more likely to cause microcephaly in the developing fetus, but poor birth outcomes and other types of birth defects have been reported associated with infection during all trimesters of gestation. Microcephaly has received much of the attention; fetal loss, intracranial calcifications, and hearing and vision defects have also been reported. It is not known how often vertical transmission –a mother with the virus transmitting it to a fetus—occurs, or how often this results in problems with the developing fetus or the pregnancy.
How should physicians counsel their patients?
Physicians should counsel pregnant women or those who want to become pregnant in the next two months that they really should not travel to areas where there is a reported threat of Zika virus transmission. If they do travel to those areas, they should wait eight weeks after returning before attempting conception.
Sexual transmission from symptomatic males has been documented, so male patients who have been symptomatic for Zika should use condoms consistently and correctly for all sexual contact for six months as a precaution to avoid transmitting the virus to a woman who may be, or may wish to become, pregnant.
What if the male traveled to an affected region, but has not been symptomatic for Zika?
Males who have traveled to an affected region but did not develop characteristic Zika signs and symptoms should use condoms consistently and correctly for all sexual contact for eight weeks after their last possible exposure.
If a patient has traveled to an affected area, what does the physician need to know?
Anyone who was pregnant when they traveled, or who became pregnant within eight weeks of returning, should be tested for Zika virus infection whether or not they developed symptoms of Zika. If the male partner of a pregnant woman traveled to an affected area, testing of the pregnant woman (and sometimes her male partner), is indicated if either one of them develops symptoms of Zika virus infection.
Patients who develop Guillain-Barré syndrome following a Zika-like infection should also be evaluated for testing.
Why shouldn’t everyone who has traveled be tested?
Testing is not as simple as marking a checkbox on a lab test order. There are two types of testing: antigen-based and antibody-based. Whether the patient is symptomatic or asymptomatic, and the timing of specimen collection, determine what type of testing needs to happen. Right now, the commercially available, antigen-based test is only good for three to four days after the onset of symptoms, so this test is completely inappropriate for patients who have no symptoms. The Massachusetts State Public Health Laboratory has the ability to run both the antigen- and antibody-based tests; preliminary positive results from the antibody test require confirmation which is currently being done by CDC. Clinicians should check the Mass. Department of Public Health clinical advisory (found under the section, “Information for Health Care Providers” on the MDPH’s Zika website) to ensure they’re ordering the appropriate test for the patient.
Physicians should also keep in mind that it’s possible that pregnant women returning from the affected regions to Massachusetts to deliver their babies here have received virtually no prenatal care, and probably haven’t been tested previously for Zika. The pediatrician may be the first health care provider to recognize that Zika is involved. Physicians should call the MDPH Epidemiology Line at 617-983-6800 to determine if testing is recommended. When Zika virus testing is appropriate, the results can help to inform the provider’s clinical decision-making and help to provide answers to parents.
Is the Department of Public Health tracking these cases?
Yes. While no single state is going to have enough data to draw all conclusions that we need to draw in order to guide clinical and prevention practices, individual states are collecting de-identified data from OB/GYN providers on pregnant moms with lab verified exposure to Zika virus. Additionally, states are working with pediatricians to follow the infants for 12 months after birth as part of participation in the U.S. Zika Pregnancy Registry being operated by CDC. Most information on the pregnant women can be collected during routine phone calls with OB/GYN providers to discuss laboratory testing and to share results. The Massachusetts Center for Birth Defects Research and Prevention within MDPH is aiding this effort by providing information on both the mother and the initial neonatal assessment as part of their routine work identifying infants with birth defects. MDPH will work with individual pediatricians to gather the requested data in as unobtrusive a manner as possible. We have been delighted by the positive relationships being developed with providers who understand the importance of collecting this information. By collecting information on the progress of pregnancies and serial assessments of infants’ health, we hope to rapidly and completely identify both the risks of infection during pregnancies and the spectrum of possible effects to infants that might include more subtle developmental problems.