Family cluster infected in Pakistan's 1st reported bird flu cases
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Authorities in Pakistan announced the country's first reported human cases of H5N1 avian flu Saturday in a cluster of family members which may have involved person-to-person transmission.
There was some confusion Saturday about how many people had tested positive for the virus, with Pakistan announcing six cases but the World Health Organization saying eight suspected cases had been identified.
The WHO said confirmatory testing must still be done. And a spokesperson for the agency said investigations are underway to try to determine how the various people became infected, but noted some human-to-human spread may have occurred.
"We can't rule it out," Gregory Hartl said from Geneva.
"There are other plausible explanations.... We don't know enough at this point. And in some of these cases, one never will know enough."
The cluster of cases involved four brothers and two cousins living in the country's North-West Frontier Province. Two of the brothers died, one without having been tested.
While the brothers who died are believed to have had at least some exposure to infected poultry, they were also known to have nursed the first case in the family, a brother who worked as a livestock official.
A doctor who treated members of the family also has tested positive for H5N1, but with a non-standard diagnostic test, Hartl said. He cautioned that further testing is needed to determine if she is indeed a case, noting she hadn't shown signs of infection.
Three people who are unrelated to the family but who were involved in culling H5N1-infected poultry in the same area have also tested positive; all are still alive. At least one of the cullers worked on the same farm as the livestock official.
Meanwhile, U.S. public health authorities have confirmed they conducted H5N1 testing on a man who had recently visited Pakistan and was complaining of mild respiratory symptoms. The man, who officials will only identify as having a link to the cluster, is said to have been concerned he might have been infected.
"The individual went to his private physician after returning from Pakistan, and discussed this with his physician," said Claire Pospisil, a spokesperson for the New York State department of health.
Pospisil said the doctor contacted the local health department in Nassau County, where the man lives, and they collected samples for testing. The tests came back negative.
David Daigle, a spokesperson for the U.S. Centers for Disease Control, said the CDC sent its plane to Albany on Dec. 8 to collect specimens for confirmatory testing. Within hours a CDC lab verified the state lab's findings.
"He was negative. There was no doubt about it," Daigle said from Atlanta on Saturday.
The initial infection in this family dates back to late October, when the livestock official became sick. It appears that it was only after two of the man's brothers fell ill and died that testing was done looking for H5N1 infection. It is believed the first positive test was received in late November.
The WHO was officially alerted Dec. 12, Hartl said.
"We feel that the Pakistanis have done everything right in terms of their response," he said, noting the country has done a "huge" amount of work to strengthen infection control and increase surveillance.
"(But) yes, they could have alerted us earlier."
Hartl said Pakistan has agreed to send specimens to the U.S. Naval Medical Research Unit in Cairo - a laboratory known as NAMRU-3 - for confirmatory testing. Those specimens are expected to be shipped Monday, he said.
In addition, people who have had contact with the cases are being traced and monitored, with close contacts being issued the antiviral drug oseltamivir (Tamiflu).
Experts from the NAMRU-3 lab are travelling to Pakistan this weekend and WHO is sending a team of two doctors with experience treating H5N1 patients as well as an epidemiologist to help with the investigation of cases.
Hartl said there don't appear to be any new infections within the family group. But he warned it is too soon to say whether this outbreak is similar to other small clusters of cases among family members or represents something larger.
"We're on our toes still, because we're still in the middle of it. We don't have enough information yet. It's not over."
Dr. Timothy Uyeki, a H5N1 expert with the CDC, cautioned against drawing premature conclusions.
"Anywhere highly pathogen influenza A/H5N1 viruses are circulating among poultry and people have direct and close contact with sick or dead poultry or poultry that are infected or wild birds that are infected, there is the potential for human cases," Uyeki said.
Small, self-limiting clusters of cases - virtually always among family members with blood ties - have occurred in many of the countries which have had human H5N1 infections, including Thailand, Vietnam, Indonesia, China, Turkey, Azerbaijan and Egypt.
While in most cases it can be almost impossible to tease out whether related cases were infected because they shared exposure to an environmental source of the virus - infected chickens, for example - in a number of cases the time gap between the onset of illness among relatives has been suggestive of human-to-human spread.
The statement from Pakistan's Health Ministry announced six infections, with five people having recovered. It was unclear who the country was counting as cases in that report.
But that figure would not include the brother who died without being tested. While his symptoms and his exposure history make H5N1 infection seem probable, without test results he cannot be added to the official case count.
Pakistan is the 14th country to announce human infections with the H5N1 virus. If these cases are confirmed, they will bring the global case count since late 2003 to nearly 350 human cases and 209 deaths.
The Pakistan outbreak is part of a flurry of recent H5N1-related human cases.
On Friday, the WHO announced that Myanmar had reported its first human case in a seven-year-old girl who fell ill in late November. She has since recovered.
Earlier this month, China reported infections in a son and father from Jiangsu province; the son died. And in recent weeks Indonesia, the country hardest hit by H5N1, has reported several human cases.
Experts who study H5N1 have come to expect this kind of upswing in viral activity at this time of year, both in poultry and in people.
"If you look at the period since November 2003 to the present we have seen increases in human H5N1 cases that are reported towards the end of the year and the early part of the new year," Uyeki said.
"And therefore it would not be surprising to begin to see an increase in human cases over the next several months."
