Mumbai under attack of 3 influenza viruses

H1N1 Has Taken Toll On More Than Seasonal Flu

Mumbai: Three types of influenza viruses are circulating in Mumbai’s air, with the most “potent and predominant” H1N1 affecting people even more than the seasonal flu, experts told TOI, providing a possible explanation for the deluge of fever and cold complaints at city hospitals.
    The observation about the three 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 % tested positive for H1N1, while about 11 % were positive for the seasonal flu. Surprisingly, 8% of the samples tested positive for influenza B, a relatively less virulent influenza strain 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, but so far there are fortunately no cases where one person is suffering from any two types together,” said Dr Abhay Chaudhary, director, Haffkine Research Institute. “Influenza H1N1 is undoubtedly the most predominant virus in the air now and it will continue to be so for some time.”
    Chaudhary added that the 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 TOI, the director of NIV, Dr A C Mishra, said that samples tested at the laboratory were primarily testing positive for H1N1. “As much as 40% of the samples are testing positive for the pandemic virus, whereas just about 10% 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.
    Virologists said they were surprised that the milder B type 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,” added Chaudhary. In 2008, incidentally, influenza B was the more dominant strain to affect Mumbai.
    But does that mean that influenza B has gained in potency? Infectious diseases expert Dr Om Srivastava said: “Clinical features of virus types are undergoing tremendous change. Even influenza B can have crippling effects, but it still remains milder than the other influenza types.”
    Some experts differ with Chaudhary and Mishra about H1N1’s dominance. Dr Jayanthi Shastri, the head of BMC’s PCR lab at Kasturba Hospital, said, “The magnitude 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 patients were tested. “Our deduction can easily be upheld as indicative of the entire community,” he said.

CATCHING THE FLU
Influenza A (H1N1)
A subtype of influenza A virus, it was earlier thought to contain gene segments from swine alone, but detailed studies showed that it had segments from swine, avian and human flu virus genes. Declared a pandemic in June last year, the virus has caused more than 17,000 deaths around the world

Symptoms | Fever, cough, sore throat, body ache, headache, chest pain, breathlessness, chills & fatigue. In certain cases, diarrhoea and vomiting is also associated with it
Positive cases in Mumbai (from April ’10) | 700 Deaths in the city (from April ’10) | 26

Influenza A
Influenza A viruses are divided into different subtypes based on two proteins on the surface of the virus, and can infect humans, horses, whales and a host of other animals. Only a few influenza A subtypes like H1N1, H1N2, and H3N2 are currently in circulation among the human population
Symptoms | Cold, fever, dizziness, lack of energy, respiratory problems and vomiting

Influenza B
Influenza B viruses are found only in humans and primarily affect children. Unlike influenza A viruses, they do not mutate or evolve fast and, experts believe, this is the reason why they have caused human epidemics but not pandemics
Symptoms | Fever, running nose, body ache, headache

Young more at risk from H1N1

Mumbai: The death of a fourmonth-old girl from Byculla of H1N1 on Tuesday once again underlined the fact that pre-existing ailments have little role to play in increasing a person’s vulnerability to the pandemic virus.
    About 217 people have died of H1N1 in the state since last year, and, experts say, a majority of them were the young. According to the National Institute of Virology (NIV) in Pune, most of those requiring hospitalisation for H1N1 belong to the age group of 20-40, while most of those queuing up for outpatient treatment are between 20 and 30 years of age. The same 20-40 age group had the maximum fatalities due to H1N1.
    The NIV’s observation was seconded by the BMC, which found that out of the 420 samples it tested for H1N1 in July this year, about 36% were between 20 and 40 years of age. Interestingly, those above 55 years made up just 4 % of the positive cases.
    “The pandemic virus has mostly affected the young. Those between 20 and 40 years have suffered the most,” said Dr A C Mishra, the director of NIV. “Also, we have enough evidence to say that no one stands an additional risk due to co-morbid conditions as even healthy are equally susceptible.”
    Experts are still in the dark as to why the pandemic virus has spared the elderly. “One explanation has been that they could have acquired some preexisting immunity as the virus could have been in circulation some decades ago,” said Dr Tanu Singhal, in charge of H1N1 cell at the Kokilaben Dhirubhai Ambani Hospital.
    Incidentally, out of the three deaths in the city this month, one was a 40-year-old lady from Kurla and another a 40-year-old man from Breach Candy. “Adult Indians do not believe in vaccination even if their mobility makes them most susceptible to the virus,” said infectious diseases consultant Dr Om Srivastava.
    Yet, the BMC maintains that co-morbid conditions have led to the maximum deaths in Mumbai. In the last 10 days, three people have succumbed to the virus and 99 have tested positive. “Close to 99% of patients who have died due to swine flu were high-risk patients like children or those suffering from pre-existing ailments,” said Dr Guirish Ambe, executive health officer, BMC.