Friday, February 28, 2014

Rate of sporadic human H7N9 infections appears to be declining

Earlier in February, I posted a chart showing the possible exponential growth of H7N9 cases in the People’s Republic of China (link). Exponential growth of infectious diseases among humans, however, can only occur if there is sustained human to human transmission. Although sporadic H7N9 cases have continued to be reported since early February, there has been no increase in number of family or local clusters that would signal sustained human to human transmission.  

Importantly, the number of sporadic H7N9 cases has recently started to decline as depicted by the 2-week moving average in the chart below.   Analysis of the data by reported onset dates indicates that the H7N9 infections started to decline about the middle of  Week 6,   about the same time that I posted the chart (link) with the projection of exponential growth of cases.

A total of 374 H7N9 cases through February 27, 2014

The World Health Organization  (WHO) has not been providing cumulative case counts of H7N9 cases in their Disease Outbreak News reports. This may be due to incomplete and inconsistent case information that has been provided to WHO by the National Health and Family Planning Commission (NHFPC) of China.

Perhaps the most accurate enumeration of H7N9 cases is provided by the Centre for Health Protection (CHP), Department of Health, Hong Kong Special Administrative Region.They report

"As of yesterday (February 27, 2014), a total of 367 human cases of avian influenza A(H7N9) have been confirmed in the Mainland, including Zhejiang (136 cases), Guangdong (81 cases), Jiangsu (42 cases), Shanghai (41 cases), Fujian (20 cases), Hunan (16 cases), Anhui (nine cases), Jiangxi (six cases), Beijing (four cases), Henan (four cases), Guangxi (three cases), Shandong (two cases), Guizhou (one case, imported from Zhejiang), Hebei (one case) and Jilin (one case).cases), Shandong (two cases), Guizhou (one case, imported from Zhejiang), Hebei (one case) and Jilin (one case)."

The 367 cases are only those reported from the mainland of the People’s Republic of China (PRC). The two imported cases reported from Taiwan and the single imported case reported from Malaysia need to be added to this total. Surprisingly, the four H7N9 confirmed cases from Hong Kong are also not included in the CHP total. 

A review of the CHP cumulative totals by province with publicly available information suggests that there is a discrepancy of one case in the count for Zhejiang Province (possibly FluTrackers’ case #182 because WHO reported this as a Shanghai case).  Also, in several reports on the initial 2013 cases from Shanghai, there is conflicting information about which cases actually died and whether or not one or more cases were only suspected cases. Confusing the situation even further is that at least one asymptomatic child from Beijing in May of 2013 is not included in the official counts.

It would be beneficial if public health agencies and international health organizations would make their line list of cases publicly available for scrutiny. In any event, through February 27, 2014, a total of 374 H7N9 cases have been officially reported since March 2013.  

Thursday, February 13, 2014

A new influenza virus, A(H10N8), is infecting people in China (map)

The first reported human case of a novel influenza A(H10N8) subtype was reported in November 2013. A 73-year-old woman from the Donghu District, Nanchang, Jiangxi Province in China experienced onset on November 28, 2013. She died nine days later on December 6, 2013.[1] 

Since then two additional human cases of H10N8 have been reported. The second is 55-year-old woman who was hospitalized on January 15, 2014. This woman is from Nanchang, Jiangxi Province.[1] And today the third human case of H10N8 has been reported, also from Nanchang, in Jiangxi Province.  This 75-year-old man died on February 8, 2014, just three days after being hospitalized.[2]

As with most novel influenza strains, H10N8 seems to be circulating among poultry populations in China resulting in sporadic jumps from poultry to humans.  With only three reported human H10N8 cases it is not possible to assess the pandemic potential of this new influenza virus.[3] Surveillance for human cases and poultry outbreaks, as well as additional genetic research, are necessary in the event this influenza virus becomes transmissible between humans.  

Thursday, February 6, 2014

H7N9 Cases in China Continue to Increase

On January 24th,  I posted a graph plotting the growth rate of H7N9 cases in China. Based on the trend (link), I estimated that between 30-40 cases of H7N9 would be reported in the coming weeks. Using current data for onset dates (through February 4, 2014), an updated plot indicates a total of 39 H7N9 cases for both Week 4 and Week 5. More than 30 H7N9 cases (without onset dates) have already been reported for Week 6. If the number of cases continues to increase at an exponential rate, more than 100 people a week will be reported as H7N9 cases by Week 7 or Week 8.  If the rate continues at its current pace, China will be experiencing an H7N9 epidemic within the near future.

Current graph of H7N9 cases through Week 5.

Monday, February 3, 2014

Map: Current Geographic Distribution of Human A(H7N9) Cases in Eastern China and Taiwan, Nov. 2013 to Feb. 2014

This map shows the geographic distribution of  human H7N9 cases by second level administrative divisions (generally prefecture-level cities) in the People’s Republic of China and Taiwan from the period of November 1, 2013 to February 3, 2014.  The map is based on geolocational information for more than 150 confirmed and reported cases since November 1, 2013.  H7N9 cases from the 2012-2013 flu season are not included on this map.  Geolocational information for individual cases is derived from numerous online reports.

Sunday, February 2, 2014

Status of the Influenza A(H7N9) virus, World Health Organization, January 31, 2014

The World Health Organization (WHO) is an arm of the United Nations and is tasked with monitoring international public health. One of the most important roles of this public health organization is to identify and track novel infectious diseases. MERS-CoV and Influenza A(H7N9) are two recent novel infectious diseases that WHO has been monitoring and tracking recently.

On January 31, 2014, The WHO published a summary of what is known about H7N9 infections, reservoirs, clinical presentation, protection, treatment, and recommendations.
WHO report: Background and summary of human infection with avian influenza A(H7N9) virus – as of 31 January 2014

This the first background and summary provided by WHO on H7N9 infections since April 3, 2013 (link). The report summarizes what is known about H7N9 at this time. It is important to understand that WHO provides factual information about the status of H7N9 cases and the disease as it is understood on the day of the report. WHO does not generally provide forecasts or speculate on the pandemic potential for a specific disease such as H7N9.

Here is a brief digest of the WHO report.

H7N9 is infecting individuals over a wide geographic area in eastern China and Taiwan. So far there is no evidence of sustained human to human transmission. WHO does not address the issue of several small family clusters that may represent human-to-human transmission.

The reservoir for the virus has not yet been formally identified but is likely avian in origin. Symptoms of H7N9 are nonspecific, such as fever, cough, and shortness of breath, all of which could be signs of a number of different respiratory infections. Laboratory testing is necessary to confirm H7N9 infection. As with other novel influenza infections, H7N9 seems to respond to treatment with neuraminidase inhibitors. Given early in the infection stage neuraminidase inhibitors can reduce disease severity and possibly increase chances of survival.

Males are infected about twice the rate of females. Although WHO indicates that the case fatality ratio (CFR) is .22 through January 28, 2014, the CFR for infected cases is uncertain because many recent confirmed cases are still hospitalized. Most of the severe reported cases are elderly individuals with chronic conditions. The median age of the cases that have died is 66 years old.

Although H7N9 vaccines are in development, none are currently available in the event of a pandemic outbreak. WHO continues to recommend a variety of prevention and control measures including hand hygiene and use of personal protective equipment (PPE) when in contact with a confirmed patient. As with any acute respiratory infection, droplet protection and the use of PPE including eye protection are recommended. Although aerosolized human-to-human transmission has not been confirmed, proper precautions to avoid aerosolized droplets is also recommended.

In the report WHO provides a number of specific recommendations for public health officials, researchers, clinicians, and laboratory personnel. WHO does not recommend any international screening or travel or trade restrictions  be applied for  H7N9 at this time. 


In summary, the lack of an identified host and the wide geographic distributions of cases suggests that H7N9 will not burn itself out soon. The fact that a few mild and asymptomatic cases have been reported provides some hope that a portion of the population has some innate or acquired immunity. H7N9 has now become another emerging infectious disease that has the potential to cause a pandemic.