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Science Technology


Influenza viruses belonging to family Orthomyxoviridae

Influenza viruses belonging to family Orthomyxoviridae

Kolkata, Mar 12 (UNI) The influenza viruses are classified into types A, B and C on the basis of their nucleoproteins.

Only types A and B cause human disease of any concern. The subtypes of influenza A viruses are determined by envelope glycoproteins possessing either haemagglutinin (HA) or neuraminidase (NA) activity.

High mutation rates and frequent genetic reassortments of these viruses contribute to great variability of the HA and NA antigens. The majority of the currently identified 17 HA and 10 NA subtypes of influenza A viruses are maintained in wild, aquatic bird populations.

Humans are generally infected by viruses of the subtypes H1, H2 or H3, and N1 or N2. Minor point mutations causing small changes (“antigenic drift”) occur relatively often. Antigenic drift enables the virus to evade immune recognition, resulting in repeated influenza outbreaks during interpandemic years.

Major changes in the HA antigen (“antigenic shift”) are caused by reassortment of genetic material from different A subtypes. Antigenic shifts resulting in new pandemic strains are rare events, occurring through reassortment between animal and human subtypes, for example in co-infected pigs.

In 2009, global outbreaks caused by the A(H1N1) strain attained pandemic proportions, gradually evolving into a seasonal epidemiological pattern in 2010.

Respiratory transmission occurs mainly by droplets disseminated by unprotected coughs and sneezes. Airborne transmission of influenza viruses occurs particularly in crowded spaces. Hand contamination followed by direct mucosal inoculation of virus is another possible source of transmission.

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14 Sep 2019 | 10:25 AM

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WHO South-East Asia Region sets 2023 target to eliminate measles, rubella

WHO South-East Asia Region sets 2023 target to eliminate measles, rubella

05 Sep 2019 | 2:11 PM

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WHO revises recommendations on hormonal contraceptive use for women at high HIV risk

WHO revises recommendations on hormonal contraceptive use for women at high HIV risk

30 Aug 2019 | 1:21 PM

Kolkata, Aug 30 (UNI) The World Health Organization (WHO) has revised its guidance on
contraceptive use to reflect new evidence that women at high risk of HIV can use any form
of reversible contraception, including progestogen-only injectables, implants and intrauterine
devices (IUDs), without an increased risk of HIV infection.

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Taking the pulse of peatland carbon emissions could measure climate impact of development: Scientists

Taking the pulse of peatland carbon emissions could measure climate impact of development: Scientists

14 Aug 2019 | 4:58 PM

New Delhi, Aug 14 (UNI) A new way to 'take the pulse' of carbon emissions could help track how the industrial development of peatlands contributes to climate change, as well as measure their recovery once it ends, according to researchers.

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Too much time on smartphones leads to obesity, deadly disease

Too much time on smartphones leads to obesity, deadly disease

27 Jul 2019 | 5:47 PM

New York, Jul 27 (UNI) Smartphone addiction could lead to serious weight gain and the onslaught of deadly diseases, according to a new study.

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