Published Date: 2010-08-12 18:00:03
Subject: PRO/EDR> Influenza B virus - India: (Mumbai)
Archive Number: 20100812.2766
INFLUENZA B VIRUS - INDIA: (MUMBAI)
A ProMED-mail post
ProMED-mail is a program of the
International Society for Infectious Diseases
Date: Wed 11 Aug 2010
Source: Times of India [edited]
[In the following report statements by officials do not clearly distinguish
the different seasonal influenza viruses and the pandemic H1N1 influenza
virus. This uncertainty is compounded by the fact that the pandemic H1N1
virus has now become the H1N1 component of the new seasonal influenza virus
vaccine. Only the statements concerning influenza B virus are unequivocal.
Mumbai under attack of 3 influenza viruses
There are 3 types of influenza viruses circulating in Mumbai's air [that
is, environment], with the most "potent and predominant" [presumably
pandemic] H1N1 [virus] affecting people even more than the seasonal flu,
experts told the Times of India, providing a possible explanation for the
deluge of fever and cold complaints at city's hospitals.
This observation about the 3 strains was made by virologists working with
Haffkine Research Institute, who, between June and August this year ,
studied 500 patients admitted for influenza-related ailments in various
hospitals. Of the 500 patients studied, the institute found that about 23
per cent tested positive for [pandemic] H1N1, while about 11 per cent were
positive for the seasonal flu [that is, non-pandemic H1N1 and/or H3N2].
Surprisingly, 8 per cent of the samples tested positive for influenza B
virus, a relatively less virulent influenza [virus] that did not surface in
Mumbai last year .
In the last 10 days, about 99 people have tested positive for H1N1 in the
city, while about 500 had tested positive in July. "Three virus types are
circulating in Mumbai air [environment], but so far there are fortunately
no cases where one person is suffering from any two types together," said
Dr Abhay Chaudhary, director of the Haffkine Research Institute. "Influenza
[pandemic?] H1N1 is undoubtedly the most predominant virus in the air
[environment] now and it will continue to be so for some time."
Chaudhary added that the [pandemic] H1N1 virus has surpassed the seasonal
flu in afflicting the wider public, a finding echoed by the National
Institute of Virology (NIV) in Pune. Speaking to the Times of India, the
director of NIV, Dr A C Mishra, said that samples tested at the laboratory
were primarily testing positive for H1N1. "As much [sic] as 40 per cent of
the samples are testing positive for the pandemic [H1N1] virus, whereas
just about 10 per cent are found to be affected by the seasonal flu,"
Mishra said, adding that traces of influenza B type were also found in
Pune's air [environment].
Virologists said they were surprised that the milder [influenza B type
virus] has managed to affect people. "It is amazing that B type has
actually managed to find its place amidst stronger strains like the
pandemic and seasonal one [H1N1?]," added Chaudhary. In 2008, incidentally,
influenza B type virus was the more dominant strain to affect Mumbai.
But does that mean that influenza B virus has gained in potency? infectious
diseases expert Dr Om Srivastava asked: "Clinical features of virus types
are undergoing tremendous change. Even influenza B virus can have crippling
effects, but it still remains milder than the other influenza types."
Some experts differ with Chaudhary and Mishra about [pandemic] H1N1's
dominance. Dr Jayanthi Shastri, the head of BMC's [Brihanmumbai Municipal
Corporation] PCR lab at Kasturba Hospital, said, "The magnitude [severity]
of the pandemic virus cannot be judged as only those who are hospitalised
are getting tested." Shastri added that there is no community sampling to
deduce such a conclusion. Mishra, however, countered that in Pune even
outdoor [that is, not hospitalised] patients were tested. "Our deduction
can easily be upheld as indicative of the entire community," he said.
[byline: Sumitra Deb Roy]
ProMED-mail rapporteur Mary Marshall
[There are 3 types of influenza virus A, B, and C. Type A influenza
viruses are further classified into subtypes according to the distinctive
nature and combinations of their virus surface proteins. Among many
subtypes of influenza A viruses, currently influenza A(H1N1) and A(H3N2)
subtypes are circulating among humans.
The A, B, and C influenza viruses are distinguished serologically on the
basis of their their matrix and nucleoprotein antigens. Influenza C virus
differs significantly from influenza A and B viruses and is much less
important in human infections. Influenza B type strains are designated in
the same way as type A strains but without H and N numbers since antigenic
shift (as a consequence of sub-unit reassortment) in these viruses has not
been observed so far. The influenza B viruses, however, do exhibit
antigenic drift similarly to the influenza A viruses, but not antigenic
shifts. The influenza B viruses tend to be associated with less severe
forms of disease, but there is some suggestion that they may be more
frequently implicated in the development of Reye's syndrome n children than
is the case with influenza A viruses. The influenza C type viruses are only
rarely isolated in humans.
Mumbai is located in the Indian state of Maharashtra and can be located
using the HealthMap/ProMED-mail interactive map of India at
<http://healthmap.org/r/008o >. - Mod.CP]