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In a previous post ( Ebola is not yet under control in any West African country ), I criticized an article that suggested that Ebola infections were declining in several countries in West Africa because the effective reproductive rate was less than 1.  The graph below depicts the number of new weekly infections in the three West African countries (Guinea, Liberia, and Sierra Leone).  Cumulatively, the number of Ebola infections is continuing to grow. The World Health Organization has indicated today ( link ) that these countries have widespread intense transmission of Ebola.  Graph notes: The data used in this graph are derived from World Health Organization and are current through August 31, 2014. Graph notes: Only cases from the Ebola outbreak in Guinea, Liberia, and Sierra Leone are used in this graph. The cases from Nigeria are not included in the week totals, but would not appreciably affect the projected rate of growth of new cases. All data are from WHO.

Since January 1, 2014, about 250 cases of MERS infection have been reported by various public health agencies and official media outlets. The number of reported cases began to increase dramatically about the 9th of April. Most of these cases (about 200) have been reported from the Kingdom of Saudi Arabia. The graph below suggests that the number of MERS cases may have peaked about April 20, and the outbreak is now being better controlled.    Notes: The date of onset for an individual case is used where available. If onset date is unavailable, the date of hospitalization or death is used. If the case is reported as asymptomatic or no other information is available, the date of report of the case is used.

The graph below shows the frequency of A(H7N9) cases by week number (based onset date) since week 47 in 2013.   The infection rate started to increase in the last week of December, 2013 and the first week of January 2014. The case count continued to climb and peak between weeks 4 through 6. Since then, the number of H7N9 cases has been declining perhaps signaling an end to the second wave of H7N9 infections in China.

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.