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Mild H5N1 in Bangladesh Increases Pandemic Concerns
Recombinomics Commentary 20:26
May 22, 2008

The DGHS, as part of its routine surveillance, sent a swab with samples from naso-pharyngeal of the 16-month-old boy to the Centres for Disease Control and Prevention in Atlanta which confirmed the H5N1 infection Wednesday.

"When the child came to us it was diagnosed with strain A positive but the H5 was found negative. However, one and a half months later when we sent the sample to Atlanta, as part of our routine surveillance, it was confirmed after culturing the virus that it was H5 positive,"

The boy, who lives in Kamalapur in Dhaka, was cured without any medicine for Influenza. He was provided with medicines for respiratory infection for 14 days...

The above comments describe the first H5N1 confirmed patient in Bangladesh.  As expected, the child had a mild case of H5N1 that initially tested negative for H5N1.  Although he was influenza A positive, he was not treated for influenza and recovered.  The H5N1 infection was discovered through routine surveillance.

The spread of mild H5N1 has been a cause for concern.  A year ago there were mild cases reported in central and southern Egypt.  These cases were not fatal and most patients did not develop pneumonia.  Thus, the H5N1 cold be more easily spread because patients were not critically ill, and testing of contacts would be rare, because most index cases would not be tested.

In Bangladesh in January H5N1 was widespread in poultry and wild birds.  Crows had tested positive throughout the country, and dead crows were reported in Dhaka.  Crows were H5N1 positive in other major cites such as Chittagong, raising concerns that human H5N1 were markedly greater than the one confirmed case.

Similarly, H5N1 was at record levels in West Bengal in January, and wild birds were dying there also.  Villagers were eating poultry that had died, and children had developed symptoms.  However, those cases were not tested.  Instead they were monitored.  India repeated announced the lack of suspect cases with pneumonia, but mild cases of H5N1 infection do not develop pneumonia.

These mild cases provide opportunities for H5N1 to adapt to human hosts by recombining with seasonal flu and acquiring the ability to transmit efficiently.  These types of adaptations in densely populated areas such as Bangladesh or eastern India are of considerable concern. 

The evidence for these infections is in the sequences of the viruses.  In Israel, H5N1 PB2 sequences have human polymorphisms.  Similarly, Tamiflu resistance in human H1N1 had become widespread through the acquisition of the polymorphisms found in resistant H5N1.  In seasonal flu isolates in Florida, and H5N1 polymorphisms has been acquired.

Thus, the mild H5N1 are flying below the detection level and lead to humanization of the H5N1 as well as transfer of avian polymorphisms to seasonal flu.

Antibody testing of patients in Bangladesh and India who had respiratory symptoms when H5N1 activity was peaking in January and February would be useful Similarly, release of H5N1 sequences from poultry and mammals, such as dogs, cats, and jackals that died after eating H5N1 infected birds would be useful.

H5N1 continues to silently spread and evolve under the poor surveillance in these affected areas.

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