Friday, February 12, 2016

Zika Virus spread 2016- Update


After the big Ebola outbreak which was initially neglected for its potential, every outbreak has been well investigated and worked on. In the latest of the series, Zika is making a lot of headlines. I have previously blogged about Zika virus. The number of recorded cases have increased over the past month. By 1st February 2016, Zika has been declared as a global emergency. WHO director general, Margaret Chan stated, "I am now declaring that the recent cluster of microcephaly and other neurological abnormalities reported in Latin America following a similar cluster in French Polynesia in 2014 constitutes a public health emergency of international concern."

Fig 1: Reported Zika cases in US.
Data as on 11 Feb 2016
At least 33 countries have reported a minimum of one case. It should be noted that by December 2015, there was a dramatic increase in reports of ZIKV infection in the Americas. Brazil is the most affected country, with preliminary estimates of 440,000 to 1.3 million by end of 2015. A recent exact statistics is not available but the number of ZKV cases reported has seen an explosive increase, especially in South American geography. The virus has also been identified in the US, with latest case identified in Maryland. That makes it a total of 21 states with a total of 59 cases have been reported in the US. All of them are imported cases. UK has reported 4 imported cases. China has also reported its first case. Though India is seen as a region with possibilities of ZKV infection, press release has stated that there has been no reported case so far.

The following Fig 2, gives a overall picture of the extent of ZKV spread on a global scale in the past 2 months. Data as on 11 Feb 2016.

Fig 2: Countries or territories with reported confirmed autochthonous cases of Zika virus infection in the past 2 months.
Photo 1: Negatively stained viral particle
with morphologic characteristics
consistent with those of Flaviviridae viruses.
More than the outbreak in itself the interest has been in its effect on Pregnancy and microcephaly in newborn neonates. Though a formal link is yet to be established, the current data superficially appears to support the association. But a article published in NEJM yesterday further adds to the evidence. The paper describes a case of a Slovenian woman from Brazil with symptoms of Zika in the 13th week of her pregnancy. After ultrasound examinations at 29 and 32 weeks showed evidence of severe brain malformations, the woman decided to have an abortion. Microbiological work up showed positive results for ZIKV on RT-PCR assay only in the foetal brain sample, (6.5×107 viral RNA copies per mg of tissue). Electron microscopy was done from homogenised brain tissue showing virus particles. See Photo 1. The question that remains to be answered is how many percentage of mothers infected with zika transmit it to the baby. Also, it is not clear as to if all babies affected with ZKV come up with microcephaly. To sum it up, as the comment in Nature News article puts it, “We have to start settling down and think about how we’re going to take care of these kids. If there is a link between Zika and microcephaly, the number of babies affected by the condition could soar as the virus spreads. We have no idea how big it’s going to get.”

Currently there is no specific treatment for ZKV or a vaccine. Many different sources has expressed an interest in developing vaccine. Bharat Biotech Ltd, has announced that they have 2 possible vaccine designs for Zika, and expect them to be tested soon. One is a recombinant virus vaccine and another is an inactivated vaccine. I have not been able to find the molecular details. With Obama administration seeking funding for research on ZKV there appears to more interest in studying ZKV infection. Much of its molecular details are unknown. Also several press releases have noted that US is probably collaborating with Brazilian institutes for a research deal on ZKV.

Global recommendations for avoiding ZKV infection are not clear. Apart from surveillance, screening of travellers to effected country is recommended. Being a mosquito borne infection all precautions such as clearing mosquito breeding sites and use of bed nets have been recommended, especially for pregnant women. Evidence of sexual transmission is not documented, though some doubts have been raised.
Fauci AS, & Morens DM (2016). Zika Virus in the Americas - Yet Another Arbovirus Threat. The New England journal of medicine PMID: 26761185

Mlakar J, Korva M, Tul N, Popović M, Poljšak-Prijatelj M, Mraz J, Kolenc M, Resman Rus K, Vesnaver Vipotnik T, Fabjan Vodušek V, Vizjak A, Pižem J, Petrovec M, & Avšič Županc T (2016). Zika Virus Associated with Microcephaly. The New England journal of medicine PMID: 26862926

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