Texas Announces Possible Local Mosquito-transmitted Zika Case

CDC Reports on Evidence of Microcephaly Developing After Birth

November 30, 2016 03:29 pm News Staff

Aedes aegypti mosquito

As of Nov 23, 4,444 cases of Zika virus have been reported to the CDC in the continental United States and Hawaii; 182 of these were spread locally by mosquitos, 36 cases are linked to sexual transmission and one was the result of laboratory exposure.

However, this total doesn't include a case currently under investigation in Texas. On Nov. 28, the Texas Department of State Health Services (DSHS) and Cameron County Department of Health and Human Services announced the state's first case of Zika virus thought to be transmitted locally by mosquito.

This affected patient is a nonpregnant female resident of Brownsville in Cameron County on the Mexican border. Lab tests of urine were positive for the virus but blood tests were negative, indicating the patient cannot spread the disease further via mosquito.

Story highlights
  • On Nov. 28, the Texas Department of State Health Services and Cameron County Department of Health and Human Services announced the state's first case of lab-confirmed Zika virus likely transmitted locally by mosquito.
  • The affected patient is a nonpregnant female resident of Brownsville in Cameron County on the Mexican border.
  • In a Morbidity and Mortality Weekly Report published Nov. 22, the CDC described research investigating 13 infants in Brazil with congenital Zika virus infection for onset of microcephaly after birth.

"We knew it was only a matter of time before we saw a Zika case spread by a mosquito in Texas," said John Hellerstedt, M.D., DSHS commissioner, in a news release.(www.dshs.texas.gov) "We still don't believe the virus will become widespread in Texas, but there could be more cases, so people need to protect themselves from mosquito bites, especially in parts of the state that stay relatively warm in the fall and winter."

Texas Response Plan

There were no additional cases of suspected local transmission as of Nov. 28, but health officials from Cameron County, the Texas DSHS and the CDC plan to continue disease surveillance activities. The DSHS has activated the State Medical Operations Center to support the response and is providing expertise, personnel and equipment for activities that include disease investigation, mosquito surveillance and public education.

The DSHS noted that travel back and forth across the Mexican border is part of everyday life in this part of Southern Texas, which could exacerbate spread of Zika virus in communities in this area. News reports have indicated Zika transmission by mosquito has already happened in multiple communities on the Mexican side of the border. Based on this knowledge, the DSHS recommended that pregnant women in Texas avoid travel to Mexico, as well as sexual contact with partners who have traveled there -- or use condoms.

The DSHS is asking health care professionals(www.texaszika.org) to consider Zika virus infection in patients who present with suspicious symptoms and order appropriate testing when indicated. Furthermore, the department recommends testing all pregnant women who have traveled to areas with active Zika transmission during their pregnancy. The DSHS also recommends testing pregnant women with no such travel history who have two or more typical Zika symptoms and who reside in Cameron, Hidalgo, Starr, Webb, Willacy or Zapata counties, as well as anyone in the state with at least three symptoms.

Is It Flu or Zika Infection? Get Help From the CDC

This is the time of year when patients with influenza-like signs and symptoms fill clinics' waiting rooms. So it's important for family physicians to remember these patients might actually be exhibiting signs and symptoms consistent with Zika virus infection, which can appear quite similar.

That's why the CDC has released a handy infographic(www.cdc.gov) that describes differences between the respective presentations of flu and Zika infection for physicians to use and pass along to their patients when helpful. The infographic offers descriptions of the two illnesses -- including differences in their constellations of signs and symptoms, modes of transmission, and disease course -- as well as prevention tips for each.

According to the DSHS website,(www.texaszika.org) Texas had recorded 257 confirmed cases of Zika virus disease as of Nov. 26. All of those cases were associated with travel, including two infants born to women who traveled during pregnancy and two people who had sexual contact with infected travelers.

Microcephaly After Birth

In other Zika-related news, a Nov. 22 Morbidity and Mortality Weekly Report(www.cdc.gov) described research the CDC conducted in collaboration with other U.S. and Brazilian researchers to evaluate 13 infants in Brazil with congenital Zika virus infection who had normal head circumference at birth (i.e., within two standard deviations or less below the mean for gender and gestational age) to determine whether they experienced onset of microcephaly after birth. The infants were born between October 2015 and January 2016.

All infants showed brain abnormalities on neuroimaging consistent with congenital Zika syndrome, including decreased brain volume, ventriculomegaly, subcortical calcifications and cortical malformations.

Eleven of the infants came to clinical attention because their head circumference at birth -- despite not meeting the clinical definition for microcephaly -- was below the level established by the Brazilian Ministry of Health as requiring further evaluation for possible congenital Zika virus infection. (This level was 33 cm before Dec. 2, 2015, and 32 cm for infants 37 or more weeks' gestational age after that date.) The other two infants with normal head circumference at birth were referred for evaluation at ages 5 and 7 months because of developmental concerns.

All evaluations were conducted between October 2015 and October 2016. Overall, head growth was documented to have decelerated as early as five months of age, and 11 of the 13 infants had microcephaly.

These findings provide evidence that among infants with prenatal exposure to Zika virus, the absence of microcephaly at birth does not exclude congenital Zika virus infection or the presence of Zika-related brain or other abnormalities.

On a related note, the graph below illustrates the relative frequency of various types of neurological problems seen among a specific population of infants born with Zika-induced microcephaly in Brazil.

The results also highlight the importance of initial and ongoing medical and developmental evaluation of infants who were exposed to Zika virus prenatally, including early neuroimaging for infants with possible congenital Zika virus infection, as described in previous CDC guidance.(www.cdc.gov)

Additionally, the CDC has released an instructional video(www.youtube.com) for health care professionals on measuring infant head circumference, which is the primary method to identify microcephaly.

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