Bird Flu Patients Need Testing Before Starting Drugs
http://www.bloomberg.com/apps/news?pid=20601080&sid=aDxoLv6PKuM4&refer=asia
By Jason Gale
Aug. 22 (Bloomberg) -- Bird flu cases may go undetected in patients who took antiviral drugs days before being tested because treating the virus may mask infection, said virologist Menno de Jong, whose team observed 18 cases in Vietnam.
Specimens should be collected from suspected cases before or soon after medicines such as oseltamivir are administered, said de Jong, head of virology at an Oxford University clinical research unit in Ho Chi Minh City. Nasal and throat swabs from Vietnamese patients who responded well to oseltamivir, marketed by Roche Holding AG as Tamiflu, were unable to detect the virus 48-to-72 hours after beginning treatment, he said.
``If a patient is on oseltamivir for three days before the first swab is taken for diagnostic testing, it's possible the result will be negative, but the patient could be infected'' with the H5N1 strain of avian influenza, de Jong said in a telephone interview yesterday.
A delayed or incorrect diagnosis is a concern for disease trackers as they monitor human cases for signs H5N1 is becoming contagious to people, not just birds. A mutated virus spreading easily from human to human might spark a pandemic that could kill millions of people.
Since 2003, H5N1 is known to have infected 240 people in 10 countries, killing 141 of them, the World Health Organization said yesterday. Almost all human H5N1 cases have been linked to close contact with sick or dead birds, such as children playing with them or adults butchering them or plucking feathers, according to the Geneva-based agency.
Early Detection
Early detection and isolation of suspected cases are important to limit the spread of the virus should it begin to spread easily between people, the WHO said last year in a recommendation of strategic actions to fight a pandemic.
The most recent H5N1 cases occurred this month in a remote village in the Garut district of Indonesia's West Java province.
Indonesia's Ministry of Health confirmed H5N1 in three villagers, two of whom died, prompting officials to investigate whether the virus had spread directly between the people. No evidence of human-to-human transmission has been found, Health Minister Siti Fadilah Supari told reporters in the capital, Jakarta, today.
Authorities distributed Tamiflu to about 2,100 villagers in Garut, the Jakarta Post reported today, citing Fatimah Resmiati, a spokeswoman from the ministry's West Java environmental health office. Indonesia, the world's fourth-most-populous country, accounts for a third of the 141 known H5N1 fatalities since 2003.
`Uncontrolled' Circulation
``The situation in Indonesia is of concern from a public health perspective,'' said Laurence Gleeson, a regional manager with the United Nations' Food and Agriculture Organization in Bangkok, in an interview. ``We know that the virus continues to circulate relatively uncontrolled in the poultry population,
and there may have been some changes in the virulence of the virus to humans in Indonesia that has resulted in this spike.''
Oseltamivir is recommended by the WHO as the first choice for doctors treating human H5N1 cases. In patients with confirmed or strongly suspected H5N1 infection, doctors should administer the drug as soon as possible, according to agency guidelines.
The efficacy of oseltamivir and other antiviral drugs that work by preventing the virus from spreading from infected cells to other cells in the body ``depends on their administration within 48 hours of onset of symptoms,'' the WHO said.
Diagnostic swabs done two days or more after the start of treatment may ``reduce the possibility of detecting the virus,'' virologist de Jong said. ``Taking a swab takes about 10 seconds. That's not a big delay.''
Dengue Fever
In Thailand, laboratory test results are pending on 100 patients under surveillance for possible H5N1, the Bureau of General Communicable Diseases in Bangkok said yesterday.
The country's first H5N1 case this year was missed for nine days, partly because the virus wasn't initially found in samples collected from the 17-year-old patient, and his symptoms were mistaken for dengue fever.
The teenager's H5N1 infection wasn't confirmed until two days after his death on July 24, the communicable diseases bureau said. Doctors suspected he had dengue hemorrhagic fever after a rapid test for influenza and several blood tests were all negative for avian flu.
The H5N1 virus hadn't been ruled because a week before his illness, the teenager had buried 10 dead chickens, touching the carcasses with his bare hands, the bureau said.
Test Results
False-negative results may have been caused by the patient's treatment with oseltamivir, said Anucha Apisarnthanarak, an infectious disease specialist and epidemiologist at the Thammasart University Hospital in Bangkok.
``We are concerned that injudicious use of antivirals might interfere'' with the amount of detectable virus material collected from nose or throat swabs, Anucha said in an e-mail.
False-negatives can also occur because replication of the virus in these parts of the upper respiratory system may be low at the time the patient was tested, he said.
A study of H5N1 cases in Vietnam, published in the Sept. 29, 2005, edition of the New England Journal of Medicine, found the virus's genetic material couldn't be detected in throat-swab samples until between two and 15 days after the patient began feeling ill. The median interval from the onset of illness to the detection of viral RNA was 5.5 days, a consultative committee to the WHO wrote in the study.
