Avian influenza virus in pregnancy

Abstract

The unprecedented epizootic of avian influenza viruses, such as H5N1, H5N6, H7N1 and H10N8, has continued to cause disease in humans in recent years. In 2013, another novel influenza A (H7N9) virus emerged in China, and 30% of those patients died. Pregnant women are particularly susceptible to avian influenza and are more likely to develop severe complications and to die, especially when infection occurs in the middle and late trimesters. Viremia is believed to occur infrequently, and thus vertical transmission induced by avian influenza appears to be rare. However, avian influenza increases the risk of adverse pregnancy outcomes, including spontaneous abortion, preterm birth and fatal distress. This review summarises 39 cases of pregnant women and their fetuses from different countries dating back to 1997, including 11, 15 and 13 infections with H7N9, H5N1 and the 2009 pandemic influenza (H1N1), respectively. We analysed the epidemic features, following the geographical, population and pregnancy trimester distributions; underlying diseases; exposure history; medical timelines; human-to-human transmission; pathogenicity and vertical transmission; antivirus treatments; maternal severity and mortality and pregnancy outcome. The common experiences reported in different countries and areas suggest that early identification and treatment are imperative. In the future, vigilant virologic and epidemiologic surveillance systems should be developed to monitor avian influenza viruses during pregnancy. Furthermore, extensive study on the immune mechanisms should be conducted, as this will guide safe, rational immunomodulatory treatment among this high-risk population. Most importantly, we should develop a universal avian influenza virus vaccine to prevent outbreaks of the different subtypes. Copyright © 2016 John Wiley & Sons, Ltd.

Pregnancy level of estradiol attenuated virus-specific humoral immune response in H5N1-infected female mice despite inducing anti-inflammatory protection

“…Sex-dependent and pregnancy-associated vulnerability to influenza infections has been well documented in humans [2,3,6,34]. Pregnant women are particularly susceptible to avian influenza H5N1 infections and are more likely to develop severe complications [3,8,9,10]. Studies have been conducted in animal models to understand sex-biased differences and pregnancy-associated susceptibility to seasonal influenza infections, mainly on H1N1 viruses [15,22,26,27,35,36].…”

Hormonal Regulation of Physiology, Innate Immunity and Antibody Response to H1N1 Influenza Virus Infection During Pregnancy

“…It remains unclear if seasonal type A (H3N2) virus infection during pregnancy causes similar poor clinical outcomes compared to the severity of complications following type A (H1N1) or type B virus infection during pregnancy ( 138 – 141 ). Lastly, the recently identified highly neurotropic avian H7N9 and H5N1 influenza A reassortants, which could potentially cause pandemics, have been shown to cause severe disease during pregnancy ( 142 – 147 ). The knowledge gained through research of the 2009 pandemic swine-derived influenza A (H1N1) virus may provide the clinical and research community with an improved capacity for the early detection of a novel pandemic virus entering a naïve pregnant population.…”

The regulated cell death at the maternal-fetal interface: beneficial or detrimental?

“…The maternal-fetal interface acts as a physical barrier between the fetoplacental unit and maternal blood, protecting against microbial invasion. While some viral infections can be transmitted vertically from pregnant women to the fetus [ 111 ], others may not have the same capability [ 112 ]. Interestingly, primary human placental trophoblast cells have demonstrated high resistance to viral infections, such as VSV.…”