CDC Reports Increase of Zika Vector in Some US States

A recent study from the Centers for Disease Control and Prevention (CDC) reports on the prevalence of Aedes aegypti and Aedes albopictus mosquitoes in the United States.

The survey and literature review, published in Journal of Medical Entomology, shares data collected between 1995 and December 2016, reporting an increase of mosquito prevalence in southern US states. Findings show that 38 new counties in the south are reporting Ae. aegypti presence — a 21% increase from the previous report – and 127 counties are reporting Ae. albopictus presence (10% increase). This information is essential as this can help scientists estimate the spread of mosquito-borne viruses such as Chikungunya, Dengue, and Zika, the latter of which has been a cause for alarm among pregnant women and their families, as local transmission of the virus is expected to increase with the start of the summer. In fact, the CDC recently published a new article highlighting findings from 7 infants who died with congenital Zika virus infection shortly after birth, in their journal Emerging Infectious Diseases.

The infants examined in the article were from a northeastern state in Brazil, Ceará, who were most likely infected during the first trimester in 2015. Zika virus infection was diagnosed in all infants after real-time reverse transcription PCR (RT-PCR) of cerebrospinal fluid and tissue tested positive for the mosquito-borne virus. The infants were also tested for Dengue virus infection, which was diagnosed in just 1 infant.

Five of the mothers had Zika-like symptoms during the first trimester of pregnancy. Of these infants, 3 were female, and one of the males had “ambiguous genitalia” that was characterized after autopsy showed undescended testes. The gestational age for these infants “ranged from 30 to 42 weeks (median 37 weeks),” with “body weight within reference range for gestational age in all except neonate 6.” In addition, all infants presented with “remarkably decreased” brain weight which emphasizes “the neurotropism of Zika virus.”

The researchers reported that these findings are in-line with those from previous cases of congenital Zika virus infection. In addition, they noted that “the constellation of neuropathologic features (ventriculomegaly, mineralized neurons, and dystrophic calcification with band-like subcortical distribution) differs” from those observed in infants who present with other congenital infections, and warrants the suspicion of a Zika virus infection.

Although microcephaly was diagnosed in 6 of the 7 infants, only 1 with seemingly normal head circumference also had “morphologic changes typical of microcephaly.” The longest-surviving infant lived for 6 days, the second longest for 48 hours, while the rest lived for less than an hour. In addition, the researchers report that a major factor in mortality was pulmonary hypoplasia “defined as lung weight:body weight ratio of <0.012 (1.2%).”

The authors conclude, “Our report confirms not only the neurotropism of the virus but also the occurrence of pathologic changes consistent with viral infection in multiple organs: liver (Councilman bodies and periportal lymphocytic infiltration), lungs (interstitial lymphocytic pneumonitis), and bladder (lymphocytic cystitis). PCR detection of Zika virus in liver, lung, and kidney tissue also strengthened our hypothesis that Zika virus can infect multiple tissues.”

Zika virus continues to be a threat to pregnant women and their developing fetuses. The CDC stresses the need for continued efforts for vector surveillance, urging state and local health departments to collaborate with “mosquito control districts” to control and prevent the spread of Aedes mosquitoes, to curb the spread of Zika and other mosquito-borne viruses.