Case-Control Study of Risk factors associated with H7N9 virus infections

(89 cases, 340 controls)

Transmission route of H7N9 virus: avian to human

• 70% of cases had contact with poultry or related environment before illness onset

• Viruses isolated from human cases shared high homology with the viruses isolated from live market with epidemiological link

• Ecological analysis on the virus in environment and virus in human: the probable virus transmission route of H7N9 virus is wholesale live market—retail live market—human

Chen Y, Liang W, Yang S, et al. Lancet,2013,381(9881):1916-1925.Bao C J, Cui L B, Zhou M H, et al. N Engl J Med,2013,368(24):2337-2339.

Poultry: Probable Source of H7N9 Virus Infection

• Probable animal reservoir： chicken, duck, pigeon• Pig: tested negative (-)

Province chicken duck pigeon environment TotalShanghai 10 0 3 7 20Jiangsu 11 0 2 0 13Zhejiang 8 2 0 0 10Anhui 0 1 0 0 1Henan 0 0 0 2 2Shandong 0 0 0 3 3Jiangxi 1 0 0 0 1Guangdong 1 0 0 0 1Fujian 0 0 0 1 1Total 31 3 5 13 52

Data Source: Animals H7N9 surveillance results released by MOA

fever

cough

sputum

shortness of breath

fatigue

emptysis

diarrhea or vomit

0 10 20 30 40 50 60 70 80 90 100

100

90

56

56

36

24

14

proportion（ %）

Gao H N, et al. N Engl J Med,2013,368(24):2277-2285.

• Whole blood cells testing: leucocytopenia (46%), lymphocytopenia (88%), thrombocytopenia (73%)

• Blood biochemistry testing: D-dimer↑(90%), LDH↑(82%), C-reactive protein↑(73%)， AST↑(66%)，myoglobin↑(55%)

• Chest X-ray：more than half cases have bilateral pneumonia (54%) , bilateral ground-glass opacities and consolidation were the most common radiologic findings

Main clinical features of human H7N9 cases（ N=111）

hemoptysis

Underlying medical conditions and complications（ N=111）

Gao H N, et al. N Engl J Med,2013,368(24):2277-2285.

underline diseases

Hypertension

Diabetes

Coronary heart disease

Immunosuppressive

COPD

Cancer

Cerebrovascular disease

Hepatitis B

Chronic kidney disease

Pregnancy

0 10 20 30 40 50 60 70 80 90 100

61

46

16

10

9

7

5

4

4

2

2

proportion（ %）

Pneumonia

ARDS

Shock

Acute renal failure

Rhabdomyolysis

0 10 20 30 40 50 60 70 80 90 100

97

71

26

16

10

Proportion（%）

Cowling BJ, Jin L, Lau EH, et al. Lancet. 2013 Jul 13;382(9887):129-37.

Comparison Epidemiology of Human Infection with H7N9 and H5N1 Viruses in Mainland China

A: Mean incubation period of H7N9 and H5N1 is 3.1 and 3.3 days

B: Time interval from onset to hospitalization for H7N9 and H5N1 cases is similar

C: Median onset to laboratory confirmation delay is shorter for H7N9 virus (due to the improved lab diagnosis capacity）D: Median time from hospital admission to death for H7N9 cases is longer (improved treatment capacity）E: Median time from hospital admission to discharge for H7N9 cases is longer

Comparison of incubation period, illness onset to admission, illness onset to laboratory confirmation, hospital admission to death, and hospital admission to discharge between H7N9 and H5N1

密度

密度

密度

密度

密度

Cowling BJ, Jin L, Lau EH, et al. Lancet. 2013 Jul 13;382(9887):129-37.

Prevention and control measures

• For provinces with case reported, or virus detected

from animal or environment samples

– Close the live poultry market

– Limit the cross-provincial poultry movement

– Poultry slaughter: once confirmed with positive H7N9

virus infection in poultry by MOA

• Health education: hand washing, behavior change

for poultry consumption and processing8

Possibility of H7N9 outbreak in future

• H7N9 virus is low pathogenic in poultry– difficult to timely detect the outbreak and effectively

prevent the transmission in poultry – Human case occurred in Hebei and Guangdong in July and in Zhejiang in October,

indicating that the virus remains circulation in poultry

• If H7N9 has similar seasonality with other avian flu– Low virus activity in hot season, but in the coming

winter and spring, virus circulation in poultry may be increasingly active

– If poultry exposure behavior of population do not change, H7N9 outbreaks in human will likely occur again

The next steps for prevention and control • Continue to enhance epidemiology and virology surveillance

– timely detect the signal of changing avian-human or human-human transmission extent of H7N9 virus,

– monitor and assess the risk of human to human transmission– Assess aerosol and other environmental routes of transmission in markets

and on farms and how to reduce risk of environmental exposure to virus– evaluate the disease severity and risk factors for infection, illness and

severity, monitor the change of antiviral resistance

• Improve the lab diagnosis capacity for human infection with avian influenza in health-care facilities

• Enhance surveillance and control on virus transmission among poultry– Improve the model of poultry farming, establish long-term

mechanism for controlling of virus transmission among poultry including environmental spread

– Forbid selling and slaughter of live poultry in wet markets at big cities in China gradually

– Poultry slaughter in designated place– Implement regular-break and strict hygiene control measures in live

poultry market if live poultry market closing is not applicable

Thanks!