Sexual Transmission of Zika Virus More Common Than Previously Reported

The CDC has released a report of 14 possible cases of sexual transmission of Zika virus infection to women; these were reported to the CDC between February 6 to February 22. In all of these cases the only risk factor for disease was having sex with a symptomatic man who had recently traveled to a region with known Zika virus transmission. The authors note that the "sexual transmission of Zika virus is more common than previously reported." 

The full report can be found here. 

To date only male to female sexual transmission has been described. It is still unclear just how long Zika virus can persist in semen. The CDC continues to recommend abstinence or condom use for men residing in or who have traveled to areas with Zika virus transmission; what is still unclear is for how long these measures are necessary to prevent Zika virus transmission.

Physicians and Social Justice

I was forwarded a link to a very compelling and thought-provoking TED talk:

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This is well worth taking a look at it, especially for healthcare providers.

Zika Virus in Semen

A new letter to the editor published online in Emerging Infectious Diseases adds to the data about Zika virus persistence in semen.

A 68 year-old man developed symptomatic Zika virus infection after traveling to the Cook Islands. Zika virus was detected in his semen by polymerase-chain-reaction testing as far out as 62 days after onset of his illness. The authors were unable to culture Zika virus directly from his semen, however.

The full text of the article is available here.

There is still much that is unknown about potential sexual transmission of Zika virus, including how commonly Zika virus persistence in semen occurs, how long this persistence is for and how commonly sexual transmission occurs.

Current recommendations from the CDC for preventing sexual transmission of Zika virus infection can be found in the February 12, 2016 Morbidity and Mortality Weekly Report (MMWR).

Zika Virus and Microcephaly: More Evidence of a Causal Link

A case report in the New England Journal of Medicine was published yesterday that provides further evidence of a link between microcephaly, brain damage and congenital Zika virus infection.

A 25 year old healthy pregnant woman developed symptoms consistent with Zika virus infection while in Brazil. Microcephaly was discovered on fetal ultrasound around 29 weeks of gestation and her pregnancy was terminated around 32 weeks given the concern for severe brain damage. A fetal autopsy was performed and revealed severe brain damage and zika virus was identified in the fetal brain tissue with reverse transcriptase polymerase-chain-reaction (RT-PCR) testing. These findings are more evidence for the connection between congenital Zika virus infection and severe brain injury and microcephaly.

The full text of the article can be found here.

More basic science and epidemiologic research is needed to better understand the relationship between congenital Zika virus infection and abnormal fetal development and to best identify strategies to prevent disease.

Congenital Zika Virus Infection and Eye Disease

A study was just published in Jama Ophthalmology looking at infants with microcephaly and presumptive congenital Zika virus infection in Brazil. Twenty-nine infants with microcephaly and presumptive congenital Zika infection were identified between December 1st and December 21, 2015.

The full text of the article can be found here.

Twenty-three of the 29 mothers (79%) reported a disease compatible with Zika infection during pregnancy; the majority (18/23, 78%) reported disease occurring in the first trimester. Ocular abnormalities were found in 10 of the 29 children (35%). These abnormalities included focal pigment mottling of the retina, chorioretinal atrophy, optic nerve abnormalities, colobomas and lens subluxation.

Congenital Zika virus infection has been linked to microcephaly, and now there is evidence that it is also associated with potential vision-threatening ocular abnormalities. More research is needed to identify the true relationship between congenital Zika virus infection and ocular abnormalities as well as to identify the best strategies to avoid congenital infection altogether. For now, ophthalmologic evaluation of infants born with microcephaly in regions with Zika transmission is warranted.

Zika Update: CDC Advice for Preventing Sexual Transmission

Areas with active Zika virus transmission in the Americas (CDC)

Guidance for preventing the sexual transmission of Zika virus was published in the Morbidity and Mortality Weekly Report on February 5th.

This article alludes to the three known cases of sexual transmission of Zika virus infection. These all involved male to female transmission with Zika virus being found in semen. In all cases the men were symptomatic.

The CDC is currently recommending abstinence or condom use for men with pregnant partners who are in or who have returned from areas where Zika virus transmission is occurring. In the above document the duration of time abstinence or condom use is recommended is not delineated. Some experts estimate up to 50% of pregnancies are unplanned, however. Given this, careful family planning consideration is warranted for all women with male partners residing in or traveling from areas with Zika transmission.

What is not known:

1) How long Zika virus can persist in semen after active infection. In one of the above cases it appeared to be present 2 to possibly 10 weeks following symptom outset; this is much longer than the virus is typically detected in the blood (less than or up to about a week).

2) How common is sexual transmission of Zika virus infection?

3) Will all men capable of sexually transmitting Zika virus be symptomatic?

4) Does female to male sexual transmission of Zika virus occur? What about male to male transmission? Or female

to female transmission?

5) How long should men who are in or who have returned from areas with Zika virus infection abstain from sex or use condoms?

At this point sexual transmission of Zika virus infection appears to be rare (with only 3 documented instances of this to date). More data is needed to answer the questions above and to best identify how to protect people living in and traveling to areas with Zika virus transmission.

More on the Zika Virus

Aedes aegypti mosquito (CDC)

Here is some more general information on the Zika virus. More information continues to emerge about this infection and the below represents a general understanding of these infections to date. 

Zika virus was first discovered in Uganda in 1947 and subsequently spread to Southeast Asia. There were outbreaks in Micronesia in 2007 and French Polynesia in 2013-2014. In May 2015 it was discovered in Brazil and now has been reported from numerous countries in South America, Central America and the Caribbean. Like Chikungunya before it, widespread infection in these areas is anticipated/ being documented. It is believed up to 4 million people in the Americas may ultimately become infected. 

Zika virus is primarily transmitted via the bites of day-biting Aedes mosquitoes, especially Aedes aegypti. These mosquitoes do exist in the United States but mostly reside in tropical and sub-tropical regions. Aedes albopictus mosquitoes are distributed more widely in the United States and are believed to be able to carry Zika virus as well but have not been implicated to the same extent as Aedes aegypti in the current outbreak. 

Only approximately 20% of people who become infected with Zika manifest symptoms. These

CDC

symptoms may include low-grade fever, conjunctivitis, rash and joint pains. These symptoms usually occur 2-12 days following a bite by an infected mosquito and symptoms typically resolve within 2-7 days. The major concern is a link to microcephaly in infants born to mothers who became infected while pregnant. In Brazil nearly 4,000 cases of microcephaly have been reported since October 2015, a greater than 20 fold increase over background microcephaly incidence. 

Zika virus infection was reported via sexual transmission (presumably via infected semen) in Texas; this is the third case of reported Zika virus transmission via sexual transmission to date. The CDC is currently recommending women who are pregnant (or trying to become pregnant) avoid travel to areas where active Zika virus transmission is occurring. They are also recommending that men who travel to transmission risk areas wear condoms for a time while in and after leaving these areas or abstain from sex. Although Zika virus appears to clear fairly rapidly from the blood of infected people it is unclear how long it may persist in semen. More information is needed to help better counsel people who have been in areas with ongoing Zika virus transmission. 

Zika Virus Update

Countries with Zika virus transmission (CDC)

Zika virus is the latest mosquito-borne viral infection to emerge in the America, close on the heels of chikungunya which was first introduced in late 2013. 

Zika virus is a flavivirus that was only recently introduced into South America and that is spreading rapidly throughout Latin America and the Caribbean. Aedes mosquitoes (especially Aedes aegypti) are day biting mosquitoes and transmit Zika virus (as well as dengue and chikungunya, among other viruses). It is believed that the incubation period for developing disease is a few days following a bite. People who develop symptoms may have mild fever, rash, conjunctivitis, headache, malaise and arthralgia. Of high concern is a significant uptick in the number of cases of microcephaly that have been detected in Brazil during the current outbreak; these appear to be related to Zika infection although a definitive causal link has not been established. Also, Zika infection has been linked to the rare, serious neurologic condition Guillain-Barre Syndrome. 

The current outbreak has been declared an emergency by the World Health Organization (WHO) and

Aedes aegypti mosquito (CDC)

the U.S. Centers for Disease Control (CDC) are currently recommending pregnant women avoid travel to countries experiencing Zika virus transmission. 

Global population growth and urbanization may have contributed to the Zika virus's emergence in the Americas. Like chikungunya just a few years before it, the virus appears to be spreading rapidly, especially in tropical and sub-tropical countries where Aedes mosquitoes exist in abundance. 

Unfortunately treatment of Zika is symptom based; no specific antiviral therapies or vaccines exist at this point. Mosquito control and bite avoidance strategies will be critical in dealing with Zika virus. Looking to the future, other viruses that are transmitted by the same mosquitos could emerge; global public health planning should anticipate these events and invest in strategies to reduce such emergence. 

Some excellent resources can be found online at the WHO site as well at CDC's site.