The Egyptian health ministry reported nine more H5N1 avian influenza infections that occurred in March to the World Health Organization (WHO), a sign that a surge in infections with the lethal virus that began last fall is still ongoing.

In an update today from its Eastern Mediterranean regional office, the WHO said the new cases lift Egypt's total for the year so far to 125 cases, 33 of them fatal. The fatality count, however, is 3 fewer than reported in the last WHO update on Mar 21. The agency said the H5N1 total for March alone is 30 cases, 4 of them fatal.

Though it is sometime difficult to gauge the number of H5N1 infections occurring in Egypt, the new total from the WHO is very close to a running tally kept by *******, an infectious disease news message board that collects, translates, and posts individual reports of H5N1 cases that come from official sources. *******' latest count, which includes some cases reported in first week of April, is at 135 cases so far this year.

The gush of cases in Egypt is unprecedented for H5N1 and has vaulted the country past Indonesia to the nation with the most cases. Indonesia still has the most deaths from the disease.

More than 330 cumulative cases

The country reported its first H5N1 cases in 2006, and the WHO said Egypt's total through the end of March is at 336 cases, 114 of them fatal. Over a third of the infections have occurred this year alone.

Only 3 months into 2015, Egypt has already reported far more infections from the disease than any other country has for an entire year. (The previous high was 61 in Vietnam in 2005.) Based on the WHO's latest update for Egypt and its last global H5N1 count on Mar 3, Egypt now accounts for 40% of the world's H5N1 cases.

Despite the onslaught of cases, the risk that H5N1 poses to the country hasn't changed, the WHO said. It added that nearly all cases in Egypt have involved close contact with infected live or dead poultry or environments contaminated with H5N1.

In the recent surge, 21 of Egypt's 29 governorates have reported infections. No significant changes in demographic or epidemiologic patterns have been seen, the WHO said. Females account for 60% of cases and have a somewhat higher death rate than males. The age-group most at risk includes adults 30 to 45 years old, followed by children younger than age 5.

With an overall case-fatality rate of 29% since activity started to rise in November, the H5N1 infections appear to be much more lethal for adults older than 45 than for young children—47% versus 7%.

Human adaptation study

Meanwhile, in research developments, a team of Japanese and Egyptian scientists who studied Egyptian H5N1 isolates collected between 2006 and 2010 from humans and poultry saw signs that the viruses can rapidly adapt to and grow in human airways by altering their hemagglutinin (HA) properties. The group published its findings in the Apr 7 edition of mBio.

The researchers' analysis of clade 2.2.1 viruses in Egypt found several HA mutations that were selected in infected humans. Some of the variants with HA mutations had evidence of increased human-type-receptor specificity and increased HA membrane fusion, both of which they said can contribute to viral replication in human airways.

They also found that the variants were more likely to have less HA stability, possibly to compensate for the receptor specificity and membrane fusion activity.

The team concluded that the findings shed more light on the mechanisms H5N1 viruses use to adapt to humans.

See also:

Apr 9 WHO update on H5N1 in Egypt

******* H5N1 case list for Egypt

Mar 3 WHO global H5N1 case count