Reporting on H7N9 cases out of Mainland China during this third winter wave has been frustratingly slow, and often devoid of useful details. In early March, after a winter of intermittent and inconsistent reporting, daily reports all but dried up (see H7N9: No News Is . . . . Curious).
Since then we’ve seen a few `bulk’ announcements of older cases, often buried in EOM epidemiological reports, and almost always with little or no epidemiological information.
Hong Kong’s CHP today reports they’ve been informed of 4 additional H7N9 cases – all apparently from between 4 and 6 weeks ago – from three mainland provinces. The fact that they are only now sharing this information with Hong Kong’s Centre For Health Protection underscores how lax reporting from the mainland has become.
First their statement, then I’ll be back with a bit more.
The Centre for Health Protection (CHP) of the Department of Health (DH) today (May 10) received notification of four additional human cases of avian influenza A(H7N9) with onset of symptoms between March 27 and April 12 from the National Health and Family Planning Commission, and again urged the public to maintain strict personal, food and environmental hygiene both locally and during travel.
The patients comprise two men and two women aged 5 to 67 and two of them (one man and one woman) died. Two cases are from Zhejiang, one is from Fujian and one is from Jiangsu.
From 2013 to date, 640 human cases of avian influenza A(H7N9) have been reported by the Mainland health authorities. Regarding the third wave in the Mainland since November 2014, a total of 200 cases have been reported, including 72 in Guangdong, 40 in Fujian, 40 in Zhejiang, 18 in Jiangsu, eight in Anhui, seven in Xinjiang, six in Shanghai, three in Jiangxi, two in Hunan, two in Shandong, one in Guizhou and one in Hubei.
Today’s announcement brings this year’s `official’ total to 200 cases – considerably more than the 1st wave of 2013 (n=133), but less than the 2nd wave (n=303).
While seemingly an improvement over last year, the continual foot dragging in reporting from the mainland and the dearth of data provided, make it a lot harder to compare this year’s wave to the first two.
Even the best disease surveillance system in the world won’t pick up all of the cases of a disease outbreak. Some cases will have mild symptoms, and never seek medical care. Some may die, untested or misdiagnosed, and never be counted.
The `official’ number is always going to be a subset of the total burden of an outbreak. The `tip of the iceberg’.
When you have good, consistent, and honest surveillance you can deal without having exact numbers. You can follow trends (increasing or decreasing case loads), geographic spread, or changes in the behavior of the virus (CFR, age or gender shifts, etc.).
Radically change the way you report cases – as we’ve seen from China during this third wave - and data comparisons become far more difficult.
It is possible (perhaps even likely) that this 3rd winter wave of H7N9 was less severe than the previous year, perhaps due to the closing of some live bird markets, the weather, or other factors.
But to make that call, you have to be comfortable with the accuracy and completeness of the data. And this year, that’s an open question.