New Influenza strain might signal the start of a pandemic
At least three Chinese patients have died as a consequence of getting infected by the newest strain of influenza and scientists are already calling for a heightened state of alert given what the strain is capable of doing. The H7N9 virus, which seems not to be able to kill animals, is fatal on humans. The H7N9 strain has never been seen before and seems to use animals as a launching pad to later infect people. Scientists refer to it as a virus with the potential to have major public health significance.
“Chinese scientists are to be congratulated for the apparent speed with which the H7N9 virus was identified,” write their counterparts at the Centers for Disease Control (CDC). It is so, because the Chinese scientists managed to sequence the whole viral genome to then make them public and available so other scientists can investigate further. “Because this H7N9 virus has not been detected in humans or animals previously, the situation raises many urgent questions and global public health concerns.”
Scientists now will concentrate on analyzing whether the virus has any chance of jumping from person to person, or if its capacity to spread is limited to going from an infected animal to a person. If the first scenario is true, it would set the stage for a potential global pandemic with a ‘sustained human-to-human transmission’. Scientists are also working on determining transmission dynamics, modes, basic reproductive number, and incubation period for the virus strain.
“It is possible that these severely ill patients represent the tip of the iceberg and that there are many more as-yet-undetected mild and asymptomatic infections,” reads a statement from the CDC. “Determining the spectrum of illness will help us understand the scope of the problem and assess severity.”
It seems that a large portion of the scientific community will dedicate much of their time to studying the H7N9 virus infection, especially its progress in people who were hospitalized on suspicions of being infected by the H7N9 virus or patients who enter a hospital with severe respiratory difficulty.
As it is usually done, healthcare practitioners may also monitor any contacts that patients infected by the H7N9 with family members or other health care workers who provided care for patients with H7N9. Scientists believe that following the chain of contact will allow them to determine if the H7N9 virus transmission is actually taking place, or whether it is limited or null. They can also determine if people who have bee exposed to the virus over extended periods of time are more susceptible to clusters of HPAI H5N1. “So far, the information provided by Chinese health officials provides reassurance that sustained human-to-human transmission is not occurring.”
According to the CDC, Chinese scientists who have treated patients with H7N9, have seen genetic characteristics that are of concern for public health. “The hemagglutinin (HA) sequence data suggest that these H7N9 viruses are a low-pathogenic avian influenza A virus and that infection of wild birds and domestic poultry would therefore result in asymptomatic or mild avian disease, potentially leading to a “silent” widespread epizootic in China and neighboring countries.”
If H7N9 virus infection is primarily zoonotic, the transmission from animals to humans may be even harder to detect as exposure to infected animals that present no symptoms of disease will silently passed it on to unsuspecting humans. But if the infection is through the HPAI H5N1 virus, the consequences will be more visible, with infected chickens falling ill and dying more rapidly.
“The gene sequences also indicate that these viruses may be better adapted than other avian influenza viruses to infecting mammals,” says the CDC.
Equally troubling is that Q226L in HA has been shown to be associated with transmission of HPAI H5N1 viruses by respiratory droplets in ferrets, one of the animal models for assessing pathogenicity and transmissibility of influenza viruses.2,3 These H7N9 viruses also possess the E627K substitution in the PB2 protein, which has also been associated with mammalian adaptation and respiratory-droplet transmission of HPAI H5N1 virus in ferrets.3
As explained before, the H7N9 virus is a new strain in the influenza family of viruses which contains genes from an ancestral avian H7N9 virus and six other genes from the H9N2 virus. A good question to ask here is whether this mixture may have occurred naturally or if it had some help from someone or something. For now, the animal hosts for the spread of the H7N9 virus seem to be birds only, but it must be determine whether the virus has the capacity to infect other animals such as pigs, which are known carriers of zoonotic infections.
Scientists have also observed that the virus is resistant to antiviral adamantanes and some susceptibility to neuraminidase inhibitors. But as it common in science, researchers do not know yet whether the resistance is a result of the viruses novelty or if it associated to the use of Oseltamivir to treat infected patients. Ongoing surveillance is crucial to assessing the emergence and prevalence of H7N9 viruses resistant to available antivirals.
The three patients who were victims of the new virus coincided in their clinical state with strong pneumonia, respiratory failure, acute respiratory distress syndrome (ARDS), septic shock, multi-organ failure, rhabdomyolysis, and encephalopathy. It is estimated that if these three patients had receive treatment with Oseltamivir, they may have had a better chance of surviving the disease, but Oseltamivir was only administered on day 7 or 8 of after the infection was detected.
For now, since H7N9 has never affected humans, scientists are clueless as to whether or not the virus will affect everyone, or if it will limit its effects to certain people according to their age, health, gender or any other variable. An analysis issued by the CDC established that existing H7 vaccines may not be able to match up with the new strain so countries and surely pharmaceutical companies are working around the clock to produce a new vaccine. Scientists are already calling for guinea pigs who can volunteer to test the new vaccine, saying that since “H7 vaccines were poorly immunogenic in humans, and clinical trials to assess the safety and immunogenicity of H7N9 vaccine candidates will be needed.”
At the end of its statement, the CDC took an opportunity to imply that a new pandemic may be closer than we all think: “The detection of human H7N9 virus infections is yet another reminder that we must continue to prepare for the next influenza pandemic.”