The World Health Organization (WHO) today detailed three local Zika cases from the same city in India, based on health ministry reports, signaling the country's first cases and further expansion of the virus.

In other developments, an update on Zika in the Americas noted the first birth defects reported from two locations, and a pair of macaque studies revealed new findings on infections during pregnancy, as well as spread through vaginal and anal sex.

Findings point to low-level transmission in India

The three infections are all from Bapunagar, in India's Gujarat state in the country's west. The cases were found during routine lab surveillance. One involves a 64-year-old man who sought care for a febrile illness, and his positive blood sample was 1 of 93 tested in the middle of February at B.J. Medical College.

Another case involves a 34-year-old woman who was tested after experiencing a low-grade fever after delivering an apparently healthy baby in early November 2016. She had a history of illness or travel during her pregnancy, and her blood test was negative for dengue but positive for Zika on polymerase chain reaction and sequence testing at the National Institute of Virology in Pune.

The third patient is a 22-year-old pregnant woman in her 37th week of pregnancy whose positive blood sample was found during surveillance in early January at an antenatal clinic.

Among response measures, the WHO said India is looking for febrile illness clusters. Mosquito testing continues, and, among recent samples tested from Bapunagar, none were positive for Zika. No microcephaly increases or clusters have been identified at sentinel sites.

The WHO said recent developments in India suggest low-level Zika transmission with the possibility of more cases.

Zika virus has been in India as far back as the 1950s, when a serology study for two other vector-borne diseases in the city of Pune found Zika in two neutralization test samples, according to a review in the September 2016 issue of the Bulletin of the World Health Organization. From the 1970s and into the 1980s, India was among the Asian countries known to have Zika in mosquitoes, and human infections in the region were thought to be sporadic, with symptoms similar to dengue or chikungunya. Experts said that fact could have explained the rare reports.

Ecuador, Barbados report first Zika birth defects

In its monthly Zika epidemiologic update yesterday, the Pan American Health Organization (PAHO) said no new countries or territories in the Americas have reported local spread of the virus. The agency added that in April Ecuador and Barbados reported their first Zika-related birth defects.

Also in April, Barbados reported its first five cases of Zika-related Guillain-Barre syndrome.

Most regions in the Americas are reporting declining cases, but upticks—mainly localized pockets of infections—have been reported recently in Belize, the Turks and Caicos, Argentina, Bolivia, Ecuador, and Peru.

Brazilian officials reported a slight increase in cases in January and February, similar to a pattern seen with chikungunya.

Monkey studies shed light on pregnancy transmission, sexual spread

Experimental Zika infection in four rhesus macaques at different stages of pregnancy found evidence of the virus in all four fetuses, suggesting that the virus passes efficiently during pregnancy, damaging tissues that support the pregnancy and developing neurological systems, a research team based at University of Wisconsin-Madison reported yesterday in PLoS Pathogens. Three of the fetuses had small heads, but not small enough to meet the human standard for microcephaly. The fetuses infected in the first trimester had unusual inflammation in the eyes, retinas, and optic nerves. The team said the similarities between monkey infections and human pregnancies affirms the usefulness of the animal model for studying potential health problems in humans and offers the possibility of studying the impact of coinfections, such as with dengue virus, during pregnancy.





In another macaque study, researchers who experimentally infected the animals nontraumatically though vaginal and anal routes found that resulting viremia levels were high enough to transmit the virus to mosquitoes. A team from the US Army Institute of Infectious Diseases reported its findings today in Emerging Infectious Diseases. The anal group included both female and male monkeys. Researchers concluded that sexual Zika spread could keep circulation going in the absence of mosquito-to-human transmission in both humans and monkeys, giving the virus a better foothold in new regions.

See also:

May 26 WHO report on three Zika cases in India

September 2016 Bull World Health Organ report

May 25 PAHO Zika update

May 25 PLOS Pathogens abstract

May 25 UW-Madison press release

May 26 Emerg Infect Dis study