Context:
- Most avian flu outbreaks in India reported from post-monsoon to pre-summer season: study.
- HPAI H5N1 viruses are constantly evolving globally through complex genetic changes, which have infected poultry, wild birds, as well as humans – study
About Influenza:
There are 4 types of influenza viruses: types A, B, C and D:
| Influenza A | Influenza B | Influenza C | Influenza D |
| Infect humans and many different animals. The emergence of a new and very different influenza A virus with the ability to infect people and have sustained human-to-human transmission, can cause an influenza pandemic. | Infect humans and many different animals. The emergence of a new and very different influenza A virus with the ability to infect people and have sustained human-to-human transmission, can cause an influenza pandemic. | Infect both humans and pigs but infections are generally mild and are rarely reported | Primarily affect cattle and are not known to infect or cause illness in people. |
Influenza type A viruses:
- They are of most significance to public health due to their potential to cause an influenza pandemic.
- Influenza type A viruses are classified into subtypes according to the combinations of different virus surface proteins hemagglutinin (HA) and neuraminidase (NA).
- So far there are 18 different hemagglutinin subtypes and 11 different neuraminidase subtypes. (need not learn the numbers for exam – given here to build a perception)
- Depending on the origin host, influenza A viruses can be classified as avian influenza, swine influenza, or other types of animal influenza viruses.
- Examples include
- Avian influenza “bird flu” virus subtypes A(H5N1) and A(H9N2)
- Swine influenza “swine flu” virus subtypes A(H1N1) and A(H3N2)
- All of these animal influenza type A viruses are distinct from human influenza viruses and do not easily transmit among humans.
- Avian influenza A viruses rarely infect people.
- Aquatic birds are the primary natural reservoir for most subtypes of influenza A viruses.
Avian influenza A viruses are classified into the following two categories: low pathogenicity avian influenza (LPAI) A viruses, and highly pathogenic avian influenza (HPAI) A viruses.
| Low pathogenic avian influenza viruses | Highly pathogenic avian influenza viruses |
| Cause either no signs of disease or mild disease in chickens/poultry. In poultry, some low-pathogenic viruses can mutate into highly pathogenic avian influenza viruses. | Cause severe disease and high mortality in infected poultry. Only some avian influenza A(H5) and A(H7) viruses are classified as HPAI A viruses. |
Read about the Spanish flu
Source: The Hindu
Previous year question
H1N1 virus is sometimes mentioned in the news with reference to which one of the following diseases?
[UPSC Civil Services Exam – 2015 Prelims]
(a) AIDS
(b) Bird flu
(c) Dengue
(d) Swine flu
Answer: (d)
Consider the following statements:
1. In tropical regions, Zika virus disease is transmitted by ‘the same mosquito that transmits dengue.
2. Sexual transmission of Zika virus disease is possible
Which of the statements given above is/are correct?
[UPSC Civil Services Exam – 2017 Prelims]
(a) 1 only
(b) 2 only
(c) Both 1 and 2
(d) Neither 1 nor 2
Answer: (c)
