Could occupational status be a clue to the infection source of A(H7N9)?

Laidback Al

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Could occupational status be a clue to the infection source of A(H7N9)?

April 24, 2013, 04:39 PM

Could occupational status be a clue to the infection source of A(H7N9)?

Of the 109 confirmed cases of Influenza A(H7N9) through April 24, 2013, electronic translation of the official reports identifies the occupational status of about 52 infected individuals. These occupation statuses can be grouped into four broad categories, farmers (12), retirees (28), poultry handling individuals (8) and an other category (4). For this discussion the poultry handler category includes the poultry workers (2), poultry truck driver (1), poultry culler (1), pigeon breeder (1), chef (1), cook (1), and butcher(1). The other category includes two factory (?) workers and two unemployed individuals. Because the occupation of more than 57 other infected individuals has not been clearly reported, the discussion here should be interpreted with caution.

Based on the limited data available, poultry industry workers have the highest case-fatality rate (CFR) among the groups, .38. The lowest CFR is .08 among farmers. Retirees, representing the largest group of individuals with an identified status (27), have a case fatality rate of .22. This CFR is comparable to the category of cases with unknown occupational status. For comparative purposes, 35 of the individuals with unreported occupations are more than 50 years old.

A report from mainland China yesterday noted that testing in live bird markets in Anhui and Shanghai shows an A(H7N9) infection range of 7-10%, resulting from tests of chickens, pigeons, and the wet market environment. Ducks were specifically reported as not testing positive (FT link).

The presence of A(H7N9) in live bird markets may indicate that domestic poultry are the infection source among poultry industry workers and, by extension, the farmers who have contact with infected poultry. However, the infection rates among retirees and elderly people may be due to some other source besides exposure in live bird markets.

The authors of Human infections with avian influenza A(H7N9) virus in China: preliminary assessments of the age and sex distribution suggest one possible source of infection for elderly males in China.

Elderly Chinese men are also well-known to be hobbyists of ornamental pet songbirds and take frequent and extended walks with their caged birds, congregating together in parks. (link)

This is an avenue worth pursuing for infection sources of A(H7N9) among elderly Chinese.

. . . Song birds are kept in bamboo cages. It is very common to see Chinese with cloth-covered cages in parks taking their birds for "walks.". . . It is not unusual to see old men riding around with bird cages attached to their bicycles. Among the singing birds found in city bird markets are rose finches, plovers, Oriental magpie robins and Mongolian larks. In a typical Chinese bird market you can [see] recently caught thrushes, skylarks and grosbeaks, looking ragged in their cruelly-small cages. Sometimes sparrows are kept on leashes by children who tame the birds by quietly stroking their heads. Budgies and minias are often raised in captivity. Exotic birds like fallvettas, leaf birds, and yhina and caught in the south and transported to the north. Link

Also, according to this same internet source,

Bird singing contests are often held on Sunday mornings, with the winners being the birds that can sing the highest number of different songs in 15 minutes. Link

The graph below compares the percentages of cases by the day of the week of the onset of symptoms for retirees and other individuals. For retirees, onset seems to peak on Mondays and Wednesdays, whereas there is little daily variation for symptom onset among the other cases. Whether this is tied to elderly congregation for song bird competitions is not known. However, the graph suggests that there is some kind of patterning in the behavior of retirees that may result in an A(H7N9) infection. Understanding that pattern may lead to the identification of an infection source among these elderly individuals.


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AlaskaDenise

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April 24, 2013, 09:33 PM

Re: Could occupational status be a clue to the infection source of A(H7N9)?

great charts Al. Thanks.

.

"The next major advancement in the health of American people will be determined by what the individual is willing to do for himself"-- John Knowles, Former President of the Rockefeller Foundation
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curiosity

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April 25, 2013, 11:05 AM

Re: Could occupational status be a clue to the infection source of A(H7N9)?

What is the breakdown of employment / trade in China. Are the percentages equal to the demographic or is there a high percentage of "farmers" ill where there would be a very small percentage of "farmers" in the trade compared to other employment? Likewise for industry, other, etc...
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Could occupational status be a clue to the infection source of A(H7N9)?

Could occupational status be a clue to the infection source of A(H7N9)?

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