Comment: Quality reporting from Priyanka Pulla in The Wire. Excerpts below, but follow the link and read the whole piece. - Ro
https://thewire.in/151409/influenza-...2-reassortant/
The Threat of Flu Pandemics is Real and India Needs a Vaccination Policy in Place Soon
BY PRIYANKA PULLA ON 28/06/2017 • LEAVE A COMMENT
Notwithstanding the recent unpredictability seen in Indian influenza seasons, we know that flu has become enough of a threat to warrant a vaccination policy.
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In tropical countries such as India, influenza often peaks during the monsoons. This has happened in enough recent years to seem like a stable trend. But in four of the five years since 2012, influenza has peaked in the summer months, grabbing news headlines and raising speculation about a viral mutation. Two of these summer outbreaks have been particularly severe: if the number of influenza cases reported by India in 2015 was higher than the number reported during the 2009 pandemic, 2017 has been following close behind.
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But are these patterns really anomalous? Researchers that The Wire spoke to pointed out that influenza surveillance before 2009 was so poor that we don't have enough data to say if monsoon peaks are the normal for India. Moreover, they said, surveillance today continues to be inherently flawed, with the Integrated Disease Surveillance Program (IDSP), India's primary disease-surveillance database, collecting more influenza patient samples during outbreak years such as 2015 and fewer in other years. This over-reporting of cases during epidemics means that those years are not comparable to quiet years. While 2015 definitely saw an extraordinary spike in the number of influenza cases, other years could have witnessed spikes that we missed because of IDSP's selective surveillance. We just don't know.
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Thankfully for India, a look at past influenza research as well as research from the rest of the world today is enlightening. It tells us four things. First: the antigenic drift that the NIV has been referring to in media reports this year is most likely a mutation that began showing up across the world in 2014. Today, we know that this mutation - christened K166Q - affects middle-aged people by lowering their immunity to currently circulating influenza strains. Therefore, the NIV's claim that no mutation has occurred doesn't hang together. Second: the immunity that people developed against the 2009 H1N1 strain has disappeared with time, and this change alone can explain the epidemics seen this year and in 2015 to a great extent. Third: while the changing seasons of influenza in India are surprising, the country has seen such flip-flops in the past. But because we don't have more data from before 2009, we don't know how common summer peaks really were. Fourth: the only dependable way to take the punch out of epidemics is vaccination - but India hasn't done much to promote it.
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In general, says James Tamerius, a medical geographer at the University of Iowa who uses mathematical models to study the seasonality of influenza, weather doesn't always predict influenza seasons in the tropics well because of how changeable weather patterns are. The tropics see both cold-dry seasons and humid-rainy weather within a space of months, each weather-type having been linked to outbreaks. "My guess is that the large swings in seasonal climate in India cause the seasonal dynamics of influenza to be inherently unstable, and this allows out of season outbreaks to occur from time to time," Tamerius told The Wire over email.
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With antigenic change and varying herd immunity mixing to unleash unpredictable epidemics in India, the question on everyone’s mind is: how do we protect ourselves? The most reliable way to contain influenza epidemics is to prevent them, say researchers. Personal hygiene, such as frequent hand-washing, can reduce viral transmission. Updated vaccinations can help induce immunity without the pain of illness. "What vaccination does is maintain herd immunity in a population so that influenza can’t come in an outbreak," says Muliyil.
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