Jan 18, 2005 (CIDRAP News) – The World Health Organization (WHO) today added two more cases to its tally of confirmed human cases of H5N1 avian flu in Vietnam, and WHO officials reportedly said another 10 suspected cases are under investigation there.

The agency increased its case count for Vietnam to 33, including 25 deaths, up from 31 cases with 23 deaths as of Jan 13. With 17 cases, including 12 deaths, in Thailand, the total since late 2003 comes to 50 cases, 37 of them fatal.

WHO spokeswoman Maria Cheng said Vietnamese officials have reported that up to 10 more suspected human cases are being investigated and that the disease has spread to all regions of the country, according to a Reuters report today. Previous reports indicated that recent outbreaks were limited to southern Vietnam.

On Jan 13 the WHO had reported 31 human cases with 23 deaths in Vietnam. The next day the agency said it had received informal reports of two more cases, one of them fatal. The fatal case was in an 18-year-old woman from the southern province of Hau Giang who had died Jan 10. The other case involved a 35-year-old woman from Tra Vinh, also in the south, who was in critical condition.

Today"e;s updated case count showed two more deaths than listed in the Jan 13 tally, but the WHO didn"e;t make clear who the other victim was.

At least four people have died of the avian virus in Vietnam since late December, according to the WHO and other reports. They have included two boys, aged 6 and 9, a 16-year-old girl, and the 18-year-old woman from Hau Giang province. Besides the 35-year-old woman in Tra Vinh, an 18-year-old woman remained in critical condition today, according to an Agence France-Presse report.

The change in the WHO case count came after media reports of several new suspected cases in Vietnam over the past few days.

A Voice of America report today said a 17-year-old boy had died of suspected avian flu Jan 15 in the southern province of Bac Lieu. The report also said a woman with suspected avian flu died in Tra Vinh on Jan 14, but it did not list her age.

In addition, a Reuters report posted on the ProMED-mail Web site yesterday said four other Vietnamese with suspected avian flu had been hospitalized Jan 15 and 16. The story said a 48-year-old man, his younger brother, and a 62-year-old man were hospitalized Jan 15 in Hanoi, and the 48-year-old subsequently died. In addition, a 14-year-old boy from Tra Vinh was hospitalized Jan 16 in Ho Chi Minh City, the story said.

But a physician from Hanoi"e;s Clinical Institute for Tropical Disease denied that the 48-year-old man had avian flu, according to a report today from the state news service Viet Nam News. The story quoted officials as saying no human cases have yet been confirmed in northern Vietnam.

Yesterday Vietnam suspended poultry imports and tightened other measures to control avian flu, according to the Vietnam News Agency and other news services. Prime Minister Phan Van Khai said imported poultry and poultry products must be seized and destroyed.

The report said a total of about 250,000 chickens, geese, and quail in 18 cities and provinces, mostly in the Mekong Delta, have been destroyed in disease-control efforts in recent weeks.

The prime minister also called for the sacrifice of all poultry flocks in which the disease has surfaced and for strict bans on the transport of poultry into and out of affected areas.

In other developments, the US Centers for Disease Control and Prevention (CDC) reiterated its concern about avian flu in an update issued Jan 14. "It is likely that H5N1 infection among birds has become endemic to the region [Asia] and that human infections will continue to occur," the CDC said.

"If these H5N1 avian viruses gain the ability for efficient and sustained transmission between humans, there is little preexisting natural immunity to H5N1 in the human population, and an influenza pandemic could result, with high rates of illness and death," the statement said.

The CDC said H5N1 vaccines are under development, but mass production "is some time off." Meanwhile, new research suggests that H5 viruses are becoming more capable of causing disease in mammals, which increases the risk that the virus will evolve and acquire the ability to spread from person to person, the agency said.